USB Instrument Driver and Instrument ... - Fremont Instruments

USB Instrument Driver

and

Instrument Boards

Fremont Instruments

Copyright © 2019 by Fremont Instruments

Rev1.3 2

Contents 1. USBID Introduction................................................................................................................................ 3

Instruments Currently Supported.......................................................................................................... 3

2. Humidity/Temperature Sensor .............................................................................................................. 5

Quick Start ............................................................................................................................................... 6

Description of All Controls ..................................................................................................................... 9

Acquisition Tab Controls .................................................................................................................... 9

Setup Tab Controls ............................................................................................................................ 12

Examples ................................................................................................................................................. 16

Specifications .......................................................................................................................................... 17

3. Thermocouple ........................................................................................................................................ 19

Quick Start ............................................................................................................................................. 20

Description of All Controls ................................................................................................................... 22

Acquisition Tab Controls .................................................................................................................. 23


Examples ................................................................................................................................................. 31

Specifications .......................................................................................................................................... 34

4. Accelerometer ........................................................................................................................................ 36

Quick Start ............................................................................................................................................. 36




Examples ................................................................................................................................................. 59

Specifications .......................................................................................................................................... 70

5. 2 Channel Strain Gauge/ Differential Amplifier ................................................................................ 71

Quick Start ............................................................................................................................................. 72




Setting Gain ............................................................................................................................................ 87

Using an External Excitation Voltage .................................................................................................. 88

Examples ................................................................................................................................................. 89

Force Transducer and Strain Gauge Basics ...................................................................................... 109

Specifications ........................................................................................................................................ 111

6. Current Sense ...................................................................................................................................... 113

Quick Start ........................................................................................................................................... 114

Description of All Controls ................................................................................................................. 118

Acquisition Tab Controls ................................................................................................................ 118

Setup Tab Controls .......................................................................................................................... 125

Current Sense Calibration .................................................................................................................. 129

Examples ............................................................................................................................................... 132

Selecting a Sense Resistor ................................................................................................................ 140

Specifications ........................................................................................................................................ 146

7. Accessories ........................................................................................................................................... 148

8. USBID and Instrument Board Care and Handling ......................................................................... 149

9. External Call of USBID Software ....................................................................................................... 150

Rev1.3 3

1. USBID Introduction

The Fremont USB instrument is a low cost complete data acquisition solution that seamlessly integrates

software and hardware. The Fremont USB instrument is Plug and Play, allowing data acquisition with no

programming skill required. Just connect two cables, start the free Fremont USBID software, and you are

ready to acquire data in a matter of seconds.

The Fremont USB Instrument is built from 2 components: a Fremont USB Instrument Driver (USBID)

and a Fremont instrument board. The Fremont USBID is a general purpose data acquisition device that

has been designed to work with all Fremont instrument boards. The Fremont instrument boards each

measure a specific property, such as temperature, acceleration, humidity and temperature, force, current,

or differential voltage.

The Fremont USBID software requires no programming skill. A single version of the software works with

all instrument boards. The USBID software detects the instrument attached and configures itself to

display controls and readouts appropriate for that instrument. The Fremont software and USBID handle

all analog and digital communication with the instrument board.

The Fremont software provides a comprehensive set of acquisition functions, tailored to each instrument.

These functions include periodic sampling at rates up to 10k samples/second, a trigger to start an

acquisition when a measured value rises above (or falls below) a threshold value, and peak or minimum

value detect. All instrument boards have an option in software for continuous data logging to a file on

your PC, allowing the collection of data for long periods. A statistics option for calculation of minimum,

maximum, mean, and standard deviation of data is available in the USBID software for accelerometers,

force/strain gauge/differential, and current sense instruments.

The USBID software has easy save of instrument configuration. Control settings can be saved and set as

the default configuration on program start. Each instrument has a unique default configuration. Multiple

configurations can be saved for each instrument.

Instruments Currently Supported

Humidity/Temperature sensor- Time between samples of 1s to 18hrs.

Thermocouple- Many types supported (J, K, N, R, S, T, E, B). Type is user selected in software.

8g accelerometer- User selected range of 2g, 4g, or 8g. Acquisition rate 1Sample/second(S/s) to 1000S/s.

24g accelerometer- User selected range of 6g, 12g, or 24g. Acquisition rate 1Sample/second(S/s) to

1000S/s.

400g accelerometer- User selected range of 100g, 200g, or 400g. Acquisition rate 1Sample/second(S/s) to

1000S/s.

2 channel force transducer/strain gauge amplifier- Acquisition rate 1S/s to 10,000S/s.

2 channel differential amplifier- Acquisition rate 1S/s to 10,000S/s.

Rev1.3 4

Current sense- Two fixed gain boards available with gain of 25 or 100. A 3.3V regulated voltage is

provided by the current sense instrument board (requires external voltage supply of 4.3V – 15V). The 25

gain instrument board can be used for current measurement up to 1000 mA and the 100 gain instrument

board is recommended for current measurements of less then 200 mA.

Chapter Format

Instrument board chapters are designed to be used as stand alone references. All functionality of the

USBID with the attached instrument board and USBID software is described in the chapter.

Each chapter starts with an overview of the capability of the particular instrument.

This is followed by a quick start guide that tells you how to connect the instrument to the USBID, start the

USBID software, and then recommendations for software settings to get you acquiring data as quickly as

possible. Quick start is essentially connect two cables, open the USBID software, and then press the

START button.

The quick start is followed by a description of all controls that can be modified as well as data outputs

with various control settings. Controls are grouped in boxes and the description of a specific control

within the box will be under the box description.

Control descriptions are followed by data acquisition examples. Finally, there is a section giving

specifications for the instrument board and USBID.

Rev1.3 5

2. Humidity/Temperature Sensor

The Humidity/Temperature Instrument acquires both temperature and humidity. The

humidity/temperature sensor board is extremely small and is attached to the USB Instrument Driver

(USBID) with a very thin and flexible cable, allowing placement of the sensor in locations where space is

at a premium.

• Small, low mass board with flexible and thin cable will minimize effects of instrument board on

measurement. Board: 10mm x 17.5 mm dimension; 0.7 gram mass. Cable: 0.13mm thick.

• Values recorded are temperature in degrees Celsius and humidity is reported as both relative humidity

(RH%) and absolute humidity (g/m^3).

• Temperature resolution is 0.01C with accuracy 0.3C. Humidity resolution is 0.025%RH with accuracy

3%. .

• Continuous data logging to PC file allows values to be collected for long time periods (thousands of

hours).

• Time between data points is set by user for an interval of 1s to 18hours.

Temperature is in degrees Celsius and humidity is reported as both relative humidity (RH%) and absolute

humidity (g/m^3). Relative humidity is the amount of water vapor present in air expressed as a percentage

of the amount needed for saturation at the same temperature. For example, if RH%=50 and T=25C, the

amount of water in the air would have to double for dew to begin to form at 25C. Absolute humidity is the

mass of water present in a cubic meter of air. The instrument measures relative humidity and temperature

directly and a calculation in software converts this to absolute humidity.

Rev1.3 6

Quick Start

Disconnect the USB cable from the USBID if connected.

Connect the Humidity/Temperature board to the USBID with a flat flexible cable (FFC). The colored tabs

on the FFC should be facing upwards as shown below in Fig. HT1.

Fig. HT1 Humidity/Temperature board attached to USBID.

Attach a USB cable to the USBID and to a USB port on your PC. An LED should now start flashing on

the USBID indicating connection to a USB port.

Start the Fremont USBID software on your PC. The software should appear as shown below in Fig.HT2.

Micro USB

Connector

FFC Inserted in FFC Connector

To insert (or remove) an FFC cable, open the FFC connector cover with your finger nail, insert (or remove)

cable with contacts down and colored tab up, then press the cover back into place.

Rev1.3 7

Fig. HT2. Fremont USBID software with Humidity/Temperature board attached to USBID.

At the upper left corner of the Fremont window you should see the textUSBID Found and HT Sensor. If

this message does not appear, make sure FFC and USB connections are made as described above.

Press the Start H/T Trace button in the H/T Acquisition box to the right of the plot area.

Data should now begin to be plotted in the chart area at the rate in the Time Between Measurements(s)

box.

Rev1.3 8

Fig. HT3. Fremont USBID software with Humidity/Temperature board attached to USBID and a

measurement in progress.

When plotted data in the chart area reaches the end of the chart area, data will overwrite data starting at

the start of the chart area.

To stop data acquisition, press Stop H/T Trace button in the H/T Acquisition box.

To save the data plotted, press the Save Current Data button at the lower left corner of the screen. Data is

saved with CSV format and can be opened using most spreadsheets.

Rev1.3 9

Description of All Controls

Tool Tray Status Boxes

There are two text boxes located at the upper left corner of the Fremont software window. The first of

these indicates the status of the USBID connection. The second indicates if an instrument is attached and

the type of attached instrument. Three combinations of messages can appear in these boxes.

Fig. HT3. The USBID is not connected to a USB port. Check the USB cable and connections.

Fig. HT4. The USBID is connected to a USB port but an instrument is not connected to the USBID with a

FFC. Check the FFC cable is correctly attached between the USBID and an instrument.

Fig. HT5. The USBID is connected to a USB port and an HT Sensor is connected to the USBID.

Acquisition Tab Controls

The following section describes the various control boxes and the functions of their buttons, check boxes,

and numeric entry fields. Text in bold face type indicates the label that is shown on the control.

Number of Points in Plot This sets the x axis plot length displayed in the plot area.

Read Single H/T Box

When Read Value button is pressed in this box the current value of humidity and temperature is read. This

value can be read while an acquisition started in the H/T Acquisition box is in progress.

Save/Open Config Box

This box is used to open or save a custom configuration. When the software is started with an attached

instrument the configuration loaded will be a default configuration located in c:\Fremont\Config. For the

humidity temperature sensor this will be HT_0.csv. When a configuration is saved all values that can be

modified will be saved. This includes boxes and radio buttons checked, and values in numeric entry

boxes.

Open When this button is pressed a dialog box pops up and you can select a configuration to load.

Rev1.3 10

Save As... When this button is pressed a dialog pops up and you can save a custom configuration. If you

would like the configuration to be the default configuration when the Fremont software starts, save the

configuration as HT_0.csv.

For the humidity/temperature sensor four values can be modified and saved in a configuration file on the

Acquisition tab: Number of Points in Plot; Display Abs. H; Log Data to PC; and Time Between

Measurements(s). In the Setup tab, values in the two boxes labeled Humidity Compensation Vals and

Temperature Compensation Vals should not be modified. These are linearization values determined by the

manufacturer.

To recover the unmodified default configuration, close the software, open the folder c:\Fremont\Config

and delete the file HT_0.csv. When the Fremont software is restarted the default configuration will be

recreated in c:\Fremont\Config and the default values loaded.

Note:

Do not modify a configuration file in a text editor. Format of the file will be changed and cannot be read

by the Fremont software. Make all changes to a configuration in the Fremont software and save changes

to a configuration file with the Save/Open Config box.

H/T Acquisition Box

The controls in this box are used to set acquisition parameters. These include start or stop an acquisition,

set acquisition rate, automatically log data to the hard drive, and display absolute humidity in the plot

area.

Start H/T Trace When this button is pressed an acquisition begins and the text in the button is changed

to Stop H/T Trace. Pressing Stop H/T Trace will stop the acquisition.

Display Abs. H This checkbox when checked will display the absolute humidity in the plot area.

Time Between Measurements(s) This control sets how frequently a humidity/temperature measurement

is performed. The sensor requires several seconds to respond to an increase in humidity. When humidity

decreases several minutes may be required for the sensor to reach equilibrium in still air. The response

time in still air to a humidity spike is shown below in Fig. HT13 in examples.

Log Data to PC When this box is checked data will be saved to c:\Fremont\Data as a CSV file (comma

separated values), readable by most spreadsheets. Use this option when a very long acquisition is made.

Otherwise, the maximum number of values saved is the length of the plot window (maximum 500

values).

The file name will be displayed below the checkbox. The file name is the date and time of the start of the

measurement (PC system time). For example, the file name 20160515125604.csv indicates that the

acquisition started in 2016(year) in 05(month, May) on 15(day) at 12(hour) 56(minute) 04(seconds).

The values saved to the file are acquisition number, time at acquisition(s), temperature(C),

humidity(%RH), and absolute humidity(g/m^3). An example of a saved data file is shown in Fig. HT6.

Rev1.3 11

n Time(s) Temperature(C) Humidity(%RH) AbsHumidity(g/m3)

0 1145.57 22.6875 56.55827 11.41902

1 1146.555 22.65625 56.48014752 11.38283

2 1147.555 22.6875 56.55827 11.41902

3 1148.557 22.71875 56.56880709 11.44163 Fig. HT6 Example of saved data file.

The zero for the time measurement value is set when the USBID is connected to a USB port. This value

can be reset to zero, current time on PC, or a custom time (see Setup tab below). The time between

measurements saved can vary by several milliseconds from the nominal Time Between Measurements(s)

due to the timing of data transfer through the USB port. This variation will average to zero for many

measurements. The time value saved is measured with a real time clock on the USBID, accurate to 0.03

ms.

Current Measurement No. This indicator shows the number of acquisitions that have been saved to the

hard drive when the Log Data to PC box has been checked.

Plot Area

Data is plotted in the plot area from left to right in the plot area. Previous data is overwritten when the plot

area is full. A red vertical cursor will move from left to right during a data acquisition. The value plotted

at the cursor is the most current value measured. The first value immediately to the right of the cursor is

the oldest acquisition.

Save Current Data

This button, located at the lower left hand corner of the Fremont software window, can be used to save

data shown in the plot area.

When the Save Current Data button is pressed a file dialog box appears. Data can be saved to either the

default location/file name or a user specified location/file name. The default file name is a date/time string

(described above in Log Data to PC) the default directory is c:\Fremont\Data. File format is CSV (comma

separated values). This format is readable by most spreadsheets.

When previous data is being overwritten in the plot area, in the saved data file, the values saved will start

at the first value to the right of the cursor in the plot (red vertical line). This is the oldest value and will be

acquisition number n=0 in the saved data file.

At the start of an acquisition, before the plot area is overwritten with new data, the first value (n=0) will

be the value in the plot area furthest to the left.

The values saved are described above in Log Data to PC.

Rev1.3 12

Setup Tab Controls The Setup tab options available for the humidity/temperature sensor are shown below in Fig. HT7.

Fig. HT7. H/T instrument setup tab controls.

Set USBID Time Box

The USBID uses a real time clock independent of the PC system clock to measure the time at data

acquisition. The time value saved is this value. The real time clock on the USBID is reset to zero

whenever the USBID is detached from a USB port. After the USBID is attached to a USB port, the clock

time on the USBID can be reset to zero, the system time of the PC to which it is attached, or a custom

time.

The Set USBID Time box is used to set the real time clock on the USBID. Within this box the time on the

USBID real time clock can be set to zero, set to the current time of the PC system clock, or set to a

custom value. The zero value of this clock is 2000, January 1, 00:00:00.

For all saved data, time data is saved in seconds. To convert the seconds data in a saved file to Date/Time

format, use the Convert Time(s) Column to Date and Time box, described below this section.

Use System Time When this radio button is checked and the Set button is pressed, the real time

clock on the USBID is set to the current time of the PC system clock. In saved data the Time(s)

value will be the current number of seconds from 2000, January 1, 00:00:00 (assuming the time on

the system clock is correctly set).

Set to Zero When this radio button is checked and the Set button is pressed the USBID real time

clock is reset to zero.

Custom When this radio button is checked and the Set button is pressed the USBID real time

clock is set to the time entered in the Year, Month, Day, Hr, min, and sec fields.

Set When this button is pressed the real time clock of the USBID is set, based on the radio button

checked.

Rev1.3 13

Read When this button is pressed the real time clock of the USBID is read and the value read is

displayed in the Year, Month, Day, Hr, min, sec, and ms fields.

Year, Month, Day, Hr, min, sec, ms These fields show the current real time clock value of the

USBID when the Read button is pressed. If the Custom radio button is checked they are used to

set the time of the USBID real time clock when the Set button is pressed. The ms field is read

only.

The figure below (Fig. HT8) shows the result when the button Use System Time is checked, the

Set button is pressed, and then the Read button is pressed.

When the Set button is pressed, the current system time on the PC is used to set the clock on the

USBID.

When the Read button is pressed, the current time value of the USBID is read, showing that the

USBID time is synchronized with the PC time.

Fig. HT8. Set USBID time to system time and then read.

Convert Time(s) Column to Date and Time Box

Fig. HT9. Control box to convert the time column in a saved file to Date/Time format.

This box is used to convert the time column of saved data from seconds to a date/time format. The default

start time for all acquisitions is seconds from the time the USBID is first powered by being attached to a

USB port. The time can be changed with the Set USBID Time box (see above) to the System Time, Zero,

or a Custom value.

When the Convert Time(s) box is used, three additional date and time columns are added to a new file

containing all of the data from the original file. The three additional columns in the new file are m/d/yr,

hr:min:s, and ms. The ordering of the month, day, and year in the date column can be specified by

checking the appropriate button. The time in the hr:min:s column is in 24 hour format.

To convert a file:

Rev1.3 14

Choose the converted date format with the three buttons at the top of Convert Time(s) to Date and Time

box. The available options are m/d/yr, yr/m/d, or d/m/yr. The date column in the converted file will use

the selected option of these three as the header.

Press the Open File button. A dialog box titled Open File will appear and you can select the file for

date/time conversion. Select the file for conversion and press the Save button.

The original dialog box will be replaced by one titled Save File with Appended Date/time. Enter a new

file name or use the default file name. The default name is system time at the time of the file conversion

(format of default file name is yyyymmddhhmmss). Press the Save button.

After a file conversion the text in the Convert Time(s) Column to Date and Time box will be changed,

showing the file opened and the new file to which data has been saved. This is shown in Fig. HT10.

Fig. HT10. Control box after a date/time conversion.

An example of the data columns in a file where time data in seconds has been converted to date and time

and appended to new file containing all of the original data is shown below in Fig. HT11.

Fig. HT11. Time in seconds converted to date and time format.

Notes:

A file to be converted can not be modified from the original saved data format before conversion. Any

modification of a file from its original format before conversion can result in an error when the file is

converted. The file to be converted can not be open in another application during conversion or an error

will occur.

n Time(s) Temperature(C)Humidity(%RH)AbsHumidity(g/m3)

0 5.78E+08 22.45558 47.31039 9.425583

1 5.78E+08 22.62718 48.34036 9.726128

2 5.78E+08 22.71298 49.4924 10.00704

3 5.78E+08 22.65936 50.53 10.18547

n m/d/yr hr:min:s ms Time(s) Temperature(C)Humidity(%RH)AbsHumidity(g/m3)

0 4/26/2018 22:28:29 660.4919 5.78E+08 22.45558 47.31039 9.425583

1 4/26/2018 22:28:30 723.389 5.78E+08 22.62718 48.34036 9.726128

2 4/26/2018 22:28:31 725.311 5.78E+08 22.71298 49.4924 10.00704

3 4/26/2018 22:28:32 725.22 5.78E+08 22.65936 50.53 10.18547

Rev1.3 15

H/T Sensor Heat Box

This control can be used to heat the humidity sensor to eliminate condensation. It can also be used

to force the H/T sensor back to equilibrium more quickly after a humidity spike than waiting for

the sensor to recover to equilibrium in still air. Figure HT12 below shows good values to use for

fast recovery after a humidity spike.

Fig. HT12. H/T Sensor Heat control box.

Pressing the Sens. Heat On button will turn on a heater within the H/T sensor for the number of

seconds in the Duration(s) control box. The Level control box sets how hot the heater is.

Rev1.3 16

Examples

This example shows a humidity spike followed by recovery in still air. High humidity (~85%) flows

across the sensor for 40s. After 40s the humidity source is removed and the sensor recovers in still air.

Fig. HT13. Response of the H/T instrument to a humidity spike. Spike is 85%RH for 40s

Followed by recovery in still air.

Rev1.3 17

Specifications

Humidity Sensor Parameter Test Condition Min Typ Max Unit

Operating Range(1) Non-Condensing 0 100 %RH

Resolution 0.025 %RH

20-80%RH 3.0 4.0

0-100%RH

Response Time(3) 1 m/s airflow 18 s

Hysteresis .0 %RH

Long Term Stability(2) 0.25 %RH/yr

%RHAccuracy(2)See figure below

Notes:

1 Recommended operating range is 20 to 80% RH (non-condensing) for 0 to 60C. Prolonged operation beyond these ranges may result in a shift of sensor reading with slow recovery time.

2 Excludes hysteresis, long term drift, and is applicable to non-condensing environments only. May be impacted by dust, vaporized solvents, or other contaminants.

3 Time for the sensor output to reach 63% of its final value after a step change.

RH Accuracy

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity(%)

RH

Meau

rem

en

t E

rro

r(%

)

Typ RH Error(±%)

Max RH Error(±%)

RH accuracy at 300 C

Temperature Sensor

Parameter Test Condition Min Typ Max Unit

Operating Range -40 85 C

Resolution 0.01 C

-10CT85C ±0.3 ±0.4 C

Maximum C

Response Time Time to 63% of final value 3 s

Long Term Stability <0.05 C/yr

See figure belowAccuracy

Rev1.3 18

Temperature Accuracy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-40 -30 -20 -10 0 10 20 30 40 50 60 70 80

Temperature(C)

T m

easu

ere

men

t E

rro

r(C

)Typ T Error(°C)

Max T Error(°C)

Real time Clock


Resolution 0.0305 ms

Accuracy -20 20 PPM

Flat Flexible Cable

Thickness: 0.15mm (0.006”)

Width: 3.5mm (0.138”)

Length: varies, 300mm (11.8”) as supplied with H/T Instrument board

Termination Style: Top on Both Sides, Backers Both Sides

Number of Conductors: 6

Pitch of Conductors: 0.5mm

Maximum FFC Cable Length: 2000mm. If this length is exceeded, the H/T sensor may not work.

H/T Instrument Board Physical Specifications (nominal)

Length: 18.4mm (0.725”)

Width: 10.15mm (0.40”)

Height: 3.5mm (0.138”)

Mass: 0.753grams

Rev1.3 19

3. Thermocouple

The thermocouple instrument measures temperature using most types of thermocouple and reports

temperature in degrees Celsius. Temperature resolution is 0.0078oC and can be used for temperature

measurements from -210oC to 1800oC, dependent on thermocouple type. Accuracy is better than 0.05%

of full scale range of the thermocouple.

• Thermocouple types supported by the instrument are K, J, N, R, S, T, E, and B.

• Data rate can be selected in software with maximum rate of 10Samples/second.

• Continuous data logging to PC file allows values to be collected for long time periods (thousands

of hours).

• Time for all saved data uses a clock independent of the PC system clock and accurately reports the

time at data acquisition.

• Real time thermocouple fault detection (thermocouple temperature out of range, thermocouple

wire broken/no thermocouple attached, thermocouple shorted to ground or +V, thermocouple

board temperature too high or too low).

Rev1.3 20

Quick Start


Connect a thermocouple to the screw terminals on the thermocouple board. Consult the thermocouple

manufacturer for correct polarity. If you are uncertain of the polarity, connect the thermocouple to the

screw terminals in either orientation and follow the instructions below. When data acquisition is started, if

an increase in temperature is reported as a decrease in temperature by the software, reverse the terminals.

Connect the Thermocouple board to the USBID with a flat flexible cable (FFC). The colored tabs on the

FFC should be facing upwards as shown below in Fig. TC1.

Fig. TC1 Thermocouple board attached to USBID.

Micro USB

Connector

FFC Inserted in FFC

Connector



Rev1.3 21



Start the Fremont USBID software on your PC. The software should appear as shown below in Fig.TC2.

Fig. TC2 Fremont USBID software with Thermocouple board attached to USBID.

At the upper left corner of the Fremont window you should see the text “USBID Found” and

“Thermocouple”. If this message does not appear, make sure FFC and USB connections are made as

described above.

In the Thermocouple Acquisition box to the right of the plot area check the type of thermocouple attached

(type B, E, J, K, N, R, S, or T) in the Thermocouple Type box. The thermocouple is attached with the

screw terminals labeled T+ and T-.

Press the Start Trace button in the Thermocouple Acquisition box to the right of the plot area.

Data should now begin to be plotted in the chart area at the rate in the Time Between Measurements(s)

box. This is shown in Fig. TC3.

Rev1.3 22

Fig. TC3. Fremont USBID software during a Real Time acquisition with a Thermocouple instrument

board attached with type K thermocouple. Thermocouple is heated rapidly then cooled in still air.

NOTE- If plotted data does not behave as expected (for example, you heat the thermocouple tip and

plotted value decreases) than flip the order of the thermocouple leads in the screw terminals T+ and T-.

When plotted data in the chart area reaches the right side of the chart area, new data will overwrite old

data in the chart starting at the left side of the chart area (oldest data is overwritten by newest data).

Newest data point is indicated by a vertical red line.

All controls will be disabled during the acquisition. To stop data acquisition, press the STOP button in the

Thermocouple Acquisition box.




Rev1.3 23

Status Boxes

The two text boxes located at the upper left corner of the Fremont software window indicate the status of

the USBID connection and the type of attached instrument. Three combinations of messages can appear in

these boxes.

Fig. TC4. The USBID is not connected to a USB port. Check the USB cable and connections.

Fig. TC5. The USBID is connected to a USB port but an instrument is not connected to the USBID with

an FFC. Check the FFC cable is correctly attached between the USBID and an instrument.

Fig. TC6. The USBID is connected to a USB port and a TC sensor board is connected to the USBID.



and numeric entry fields. Text in bold face type indicates the label that is shown on the control.

Number of Points in Plot This sets the x axis plot length displayed in the plot area. This is also the

number of points saved with “Save Current Data” button. To save longer sets of data check the box “log

Data to PC”.

Save/Open Config Box

This box is used to open or save a custom configuration. When the software is started with an attached


thermocouple instrument this will be TC_0.csv. When a configuration is saved all values that can be

modified will be saved. This includes all boxes and radio buttons checked, and values in numeric entry

boxes.




configuration as TC_0.csv.

For the thermocouple instrument five values can be modified and saved in a configuration file on the

Acquisition tab: Number of Points in Plot; Thermocouple Type; Samples Averaged; Time Between

Measurements(s); and Log Data to PC.

Rev1.3 24


and delete the file TC_0.csv. When the Fremont software is restarted the default configuration will be


Note:




Thermocouple Acquisition Box

This box is used to set parameters during an acquisition. All acquisition parameters must be set prior to

the start of an acquisition. Parameters cannot be changed while an acquisition is in progress.

Start Trace Pressing this button will star an acquisition. When the button is pressed, the text on

the button will change to Stop Trace. To end an acquisition press the Stop Trace button.

Thermocouple Type The buttons in this box are used to set the type of thermocouple attached.

This value must be set by the user since the USBID cannot automatically detect the type of

thermocouple attached.

Samples Averaged sets the number of samples averaged for the reported temperature value. The

number of samples averaged will not affect acquisition rate but will affect the update rate of

acquired values. For example, if Samples Averaged is set to 16 and Time Between

Measurements(s) is set to 0.1, the same value may be reported for 300ms. This will appear as steps

in acquired data. For Time Between Measurements(s) values of less than 1, Samples Averaged

should be decreased. Decreasing the number of Samples Averaged will decrease time response but

will also decrease accuracy. The table below gives a guide line for samples averaged versus Time

Between Measurements(s) to avoid stepping.

Time Between Measurements(s) Samples Averaged

0.1 1

0.2 2

0.3 4

0.4 8

0.5 8

0.6 8

0.7 and greater 16

Time Between Measurements(s) sets the number of seconds between acquisitions. This is also

the rate at which data is plotted and optionally saved. The up down buttons at the right of the

control increase or decrease the value in increments of 1s. To increment this value for fractional

values of a second, highlight the value in the control and type the value manually. Range of the

control is 0.1s to 65535s with a resolution of 0.1s. The time entered in the Time Between

Measurements(s) box is the approximate time value between measurements and can differ from

the actual value between measurements by up to 15ms. The actual value of time at measurement is

measured by the USBID and reported in the time column of a saved measurement.

Rev1.3 25

Log Data to PC When this box is checked, all data acquired is automatically saved to a file on the

PC. The location and file name of the saved data is indicated in the text below the box when the

box is checked and “Start Trace” button is pressed.

The file name is the date and time of the start of the measurement (PC system time). For example,

the file name 20160515125604.csv indicates that the acquisition started in 2016(year) in

05(month, May) on 15(day) at 12(hour) 56(minute) 04(seconds). The file format is CSV, Comma

Separated Values, readable by most spreadsheets.

The values saved to the file are acquisition number, Time(s), TC Temperature(C), ColdJuncT(C),

and Fault. An example of a saved data file is shown in Fig. TC7.

Fig. TC7. Example of saved data format.

In saved data: n is the acquisition number; Time(s) is the actual time of the measurement

(measured by a real time clock on the USBID (see Setup tab instructions below for setting this

clock)); TC Temperature(C) is the temperature of the thermocouple tip; ColdJunctT(C) is the

temperature of the thermocouple board; Fault is a binary number which enumerates all faults

detected (see Thermocouple Fault Detection below). Note that the time between the first and

second measurement can be 1s greater than the time specified in Time Between Measurements(s)

box.

To the right of the column header values is information giving the type of thermocouple and

samples averaged.

If you wish to look at the data in this file while an acquisition is in progress, copy the file to a new

folder and then open data file in the new folder. If you open the file located in c:\FremontData

while an acquisition is in progress, a sharing violation will occur when the next data point is

saved.

Current Measurement No. This displays the total number of points that have been measured and

saved to PC memory from the start of the acquisition. This value is only incremented when the log

Data to PC box is checked.

Temperature This indicator displays the most recently measured value of the thermocouple

temperature.

CJ Temperature this indicator displays the ambient temperature of the thermocouple board.

Thermocouple Fault Detection The indicator at the bottom of the Thermocouple Acquisition box

indicates the status of the thermocouple and thermocouple board. If the box is green, no fault has

been detected with the thermocouple and thermocouple board. If the box is red, four messages can

be shown in this box:

Open Thermocouple: No thermocouple is attached or the thermocouple wire is broken.

Rev1.3 26

Over/Under Voltage: The thermocouple is grounded or a voltage is being applied to the

thermocouple.

TC Out of Range: The temperature at the thermocouple exceeds its rating.

CJ Out of Range: The temperature of the thermocouple board is either too high or low.

To see a complete list of faults, save data. When data is saved, all thermocouple faults are reported

in the Fault column. Values in the fault column are reported in decimal and must be converted to

binary to determine the specific fault(s). When converted to binary format, 0 indicates no fault, 1

indicates a fault. The format of the fault bits is shown in Fig. TC8.

Fig. TC8. Format of binary data in Fault column of saved data.

Fig. TC9. Examples of several faults in the binary format used in saved file Fault column (Fault

Description is not in saved data file).

Make sure the type of attached thermocouple has been checked in the Thermocouple Type box

before the start of an acquisition, otherwise reported faults may be incorrect.

If the TC Open bit is set (Open Thermocouple), a TC Range (TC Out of Range) fault will also

occur. TC Open indicates either a thermocouple is not attached or a thermocouple wire is broken.

When the TC Open fault occurs, check the attachment of the thermocouple at the screw terminals

and the integrity of the thermocouple wires.

OV/UV (Over Voltage/Under Voltage) indicates that the thermocouple is at a voltage either

greater than the voltage used by thermocouple board (3.3V) or at a voltage lower than the ground

value of the thermocouple board.

TC Low indicates that the thermocouple is at a value lower than its nominal rating. For example,

this would indicate a temperature below -200oC for a type K thermocouple (a type K is rated for a

temperature range of -200oC to 1372oC).

TC High indicates that the thermocouple is at a value higher than its nominal rating. For example,

this would indicate a temperature above 1372oC for a type K thermocouple (a type K is rated for a

temperature range of -200oC to 1372oC).

CJ Low indicates that the Thermocouple board is at a temperature below its rating for the attached

type of thermocouple. For types E, J, K, N, and T the minimum value is -55oC. For types R and S

the minimum value is -50oC. For type B the minimum value is 0oC. For best accuracy, the

thermocouple board temperature should be 25oC. The USBID board should always be in the range

of -40oC to 85oC.

Rev1.3 27

CJ High indicates that the Thermocouple board is at a temperature above its rating for the attached

type of thermocouple. For all types this value is 125oC. For best accuracy, the thermocouple board

temperature should be 25oC. The USBID board should always be in the range of -40oC to 85oC.

TC Range indicates that the measured temperature value of the attached thermocouple temperature

is either above or below its rated temperature range (see above TC Low and TC High).

CJ Range indicates that the measured value of the thermocouple board is outside the range

allowed by the attached thermocouple type (see above CJ Low and CJ High).

Rev1.3 28

Setup Tab Controls

The available controls in the setup tab are used to set the clock on the USBID and to convert the Time(s)

column in a saved data file to date/time format. The available controls on the setup tab are shown in Fig.

TC10.

Fig. TC10. Setup Tab Controls.

Set USBID Time Box





time.















checked.






only.

Rev1.3 29

The figure below (Fig. TC11) shows the result when the button Use System Time is checked, the



USBID.



Fig. TC11. Set USBID time to system time and then read.


Fig. TC12. Control box to convert the time column in a saved file to Date/Time format.




or a Custom value.





To convert a file:






Rev1.3 30





showing the file opened and the new file to which data has been saved. This is shown in Fig. TC13.

Fig. TC13. Control box after a date/time conversion.


and appended to new file containing all of the original data is shown below in Fig. TC14.

Fig. TC14. Time in seconds converted to date and time format.

Notes:




will occur.

Rev1.3 31

Examples Example1- Fig.TC15 shows the software window during a data acquisition. Data is being saved to a file

(log Data to PC box checked), Thermocouple Type is K, the number of Samples Averaged is 16, and

Time Between Measurements(s) is 1 second. Note that all controls are disabled until the Stop button is

pressed.

Fig.TC15. Screen shot of a thermocouple data acquisition.

Rev1.3 32

Example2- Fig.TC16 shows the temperature profile in an empty electric home oven. The cycle shown is

heating from room temperature to 3500F with temperature maintained at 3500F for 1.5 hours. The

temperature is than set to 2000F and temperature is recorded for an additional 2 hours, showing the time

response during cooling and stabilization at the new set point.

170

180

190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340

350

360

370

380

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230T ime(minutes)

Temperature(F)

T(F ) corrected

S et P oint

Fig.TC16. Temperature in GE Profile oven during heating to 3500F and then cooling to a set temperature

of 2000F.

The most noticeable thing in Fig.TC15 is that when starting the oven cold, after reaching the set point, the

oven temperature dips 650F below the set point before again seeking the set point and it takes 20 minutes

for it to again reach the set point.

Rev1.3 33

Example3- Fig.TC17 shows the temperature profile for the same oven in a cooking example. After

reaching the set point of 3500F, indicated by the oven display, the oven is opened and a pan with a

7lb(3.2kg) casserole is added. The temperature of the casserole when placed in the oven is 400F(4.50C).

170

180

190

200

210

220230

240

250

260

270

280

290

300

310

320330

340

350

360

370

380

0 10 20 30 40 50 60 70 80 90Time(minutes)

Tem

pera

ture

(F)

T(F)

Set Point

Fig.TC17. Temperature in GE Profile oven during heating to 3500F and then adding a thermal load.

Looking at the above example you will see that after the oven reaches its set temperature the oven

temperature is not regulated for about 10 minutes. During this time, temperature drops 900F below the set

temperature. When active control is resumed, the oven temperature takes an additional 20 minutes to

reach the set point, a total of 30 minutes when the oven is below the set point.

With a minimally more intelligent temperature algorithm, temperature drop for example3 would be 400F

below the set point and recovery time to the set point would be 10 minutes. This just requires removing

the 10 minutes of dead time after the oven reaches its set point and allowing active control of the oven

(shown for Time=20-90 minutes).

With a much more intelligent temperature algorithm used, something like a proportional-integral-

derivative(PID) driver, temperature would be constantly monitored and when temperature falls below or

rises above the set point there would be an immediate response. With a properly implemented PID

controller, oven temperature could probably be maintained to within 50F of the set point.

Rev1.3 34

Specifications Thermocouple Resolution: 0.0078125oC

Parameter TC Board Temperature Typ Unit

-20C to 85C 0.7 C

-40C to 105C 1 C

-55C to 125C 2 C

Thermocouple Accuracy

, Real time Clock


Resolution 0.0305 ms

Accuracy -20 20 PPM

Flat Flexible Cable


Width: 3.5mm (0.138”)

Length: 300mm (11.8”) as supplied with H/T Instrument board




TC Instrument Board Dimensions (nominal)

Board Dimensions, inches(mm)

Mass: 3.05 grams

Hole Diameter: 0.125(3.18), clearance for 4-40 or M3.0. Socket cap screws recommended for mounting.

0.50 (12.7)

0.75 (19.05)

0.125 (3.17)

1.10 (27.94)

0.40 (10.16)

Rev1.3 35

USBID Board Dimensions (nominal)


Mass: 2.35g


0.75 (12.7)

1.00 (25.4)

0.125 (3.17)

.080 (20.32)

0.125

(3.17) (10.

16)

Rev1.3 36

4. Accelerometer

The Accelerometer Instrument is a 3-axis accelerometer, measuring acceleration on three perpendicular

axes (X,Y,Z) with ranges from 2g to 400g. Three types of accelerometer are available with ranges from

2g to 400g. This chapter applies to all three accelerometers. 1g =9.8m/s2, the acceleration due to gravity.

• All accelerometers have a range selected in software.

• 8g accelerometer ranges are 2g, 4g, or 8g.

• Resolution of 0.001g to 0.004g (depends on range selected).





• Small, low mass accelerometer board with flexible and thin cable will minimize effects of instrument

board on measurement. Board: 10mm x 17.5 mm dimension; 0.7 gram mass. Cable: 0.13mm thick.

• Acquisition rates from 1Sample/second(S/s) to 1,000S/s. One sample contains 6 values: sample

number, time at sample, X acceleration, Y acceleration, Z acceleration, and magnitude of acceleration.

• Automated accelerometer calibration routine in software for all axes. Once these values are set, all

plotted or saved samples are scaled to these values

• Acquisition types:

• Real Time- Continuous acquisition of data at ~30S/s.

• Waveform- One shot data acquisition of up to 300 samples at up to 1000S/s.

• Waveform On Trigger- One shot data acquisition of up to 300 samples when trigger conditions are

met at up to 1000S/s.

• Statistics- Statistics are collected for a specified number of samples (up to 300) at a specified data rate,

up to 1000S/s. The statistics reported are maximum, minimum, mean, and standard deviation for each

of the 3 axes for the specified number of samples. Maximum magnitude of acceleration is also

reported. Data can be logged to a PC, allowing an infinite number of points to be collected.

• Peak Detect on Trigger- Detects the peak value after a trigger event. Scan length for peak, number of

peaks to detect, and trigger level set in software.

• Shock and free fall detect.

• Acquisitions can be triggered by a shock or free fall.

• Advanced Acquisition features:

• Acquire multiple waveforms periodically or when trigger condition met.

• Up to 20,000 samples saved (100 waveforms of 200 samples, 200 waveforms of 100 samples, 400

waveforms of 50 samples,...).

• For periodic waveforms, period between waveforms can be set as either seconds or samples.

• Acquire up to 10,900 peaks.

• Masking feature for peak detect on trigger and waveform on trigger.

• Post Trigger Mask- a delay after a trigger event before a data acquisition starts.

• Post Waveform Mask- a delay after a data acquisition before the trigger is enabled.

Quick Start

Rev1.3 37

Install the Fremont USBID software on your PC.


Connect the Accelerometer board to the USBID with a flat flexible cable (FFC). The colored tabs on the

FFC should be facing upwards as shown below in Fig. AC1.

Fig. AC1. Accelerometer board attached to USBID.

Micro USB

Connector




Rev1.3 38

Attach a micro USB cable to the USBID and to a USB port on your PC. An LED should now start

flashing on the USBID indicating connection to a USB port.

Start the Fremont USBID software on your PC. The software should appear as shown below in Fig.AC2.

Fig. AC2. Fremont USBID software with a 24g accelerometer board attached to USBID.

Check the Real Time button in the Accelerometer Acq box to the right of the plot area and press the Start

button. Rotate the accelerometer and you should see X, Y, Z, and Magnitude traces in the plot area similar

to that shown below in Fig. AC3 (for a 24g accelerometer).

Rev1.3 39

Fig. AC3. Fremont USBID software during a Real Time acquisition with a 24g accelerometer board

attached to USBID.



Newest data point is indicated by a red diamond.

All controls will be disabled during the acquisition. Press the Stop button in Accelerometer Acq box to

stop the acquisition and enable controls.



The magnitude of the acceleration along any axis may be off by up to 0.08g without calibration for the

24g accelerometer. See below for calibration of your accelerometer.

Rev1.3 40





these boxes.

Fig. AC4. The USBID is not connected to a USB port. Check the USB cable and connections.

Fig. AC5. The USBID is connected to a USB port but an instrument is not connected to the USBID with a

FFC. Check that the FFC cable is correctly attached between the USBID and an instrument.

Fig. AC6. The USBID is connected to a USB port and an accelerometer board is connected to the USBID.


Accelerometer Configuration Box

Range- Check a button in this box to specify the desired acceleration range of the attached accelerometer.

For best resolution choose the smallest range so that the range is not exceeded during a measurement. For

a 24g accelerometer available ranges are 6g, 12g, or 24g. For a 400g accelerometer available ranges are

100g, 200g, or 400g.

Data Rate(S/s)- The buttons in this box specify the number of samples measured per second. One

sample contains 6 values: sample number, time at sample, X acceleration, Y acceleration, Z acceleration,

and magnitude of acceleration. The value specified by Data Rate is approximate. To see actual data rate,

save an acquired waveform using Acquire Waveform or Waveform on Trigger and look at the time(s)

column in the saved file. Actual data rate can be calculated from the difference in the time values in the

time(s) column. All time data saved uses the high accuracy timer on the USBID and not the nominal

sample rate specified in the Data Rate(S/s) box.

Rev1.3 41

The table below shows actual data rate for one accelerometer compared with data rate specified in the

Data Rate(S/s) box. Data was measured for 300 samples (WF Length(S)) and Measured Val(S/s), shown

below, was calculated using the time values saved from the data file created on Save Current Data button

press. The values shown in the Measured Val(S/s) are calculated using the high accuracy timer on the

USBID. Actual data rates for your device may vary from those shown below. The data in the Time(s)

column of a saved data file shows the actual data rate of your accelerometer and may differ from the value

checked in Data Rate(S/s) box.

Data Rate(S/s) Measured Val(S/s)

1 1.143

2 2.255

5 5.4

10 10.091

50 49.998

100 99.85

400 399.463

1000 561.501

Some time averaging is used in the accelerometer so lower data rates will have lower noise (compare a

Real Time measurement at 50Hz with one at 1000Hz to see this).

Trigger Box

The values in this box are used to set the axes that can be set as a trigger, if a trigger occurs when the

acceleration along an axis is greater or less than the trigger level, the threshold value(Trigger Level) when

a trigger occurs, and the logic type for the selected axes (AND or OR).

OR- When this radio button is checked OR logic is used for the checked axes buttons. The Trigger

Level must be satisfied for any checked axes for a trigger to occur.

AND- when this radio button is checked AND logic is used for the checked axes boxes. The Trigger

Level must be satisfied for all checked axes for a trigger to occur.

For example, if AND, xHi, and yHi are checked, Range = 6g, and Trigger Level = 50%, the magnitude

of the acceleration along both the X and Y axes must exceed 3g for a trigger to occur. This option

should be carefully considered before using when more then 2 axes are selected and Trigger Level is

greater than 1g (if Trigger Level is 3g and xHi, yHi, and Zhi are selected, it would be very difficult to

produce an acceleration of 3g along all axes simultaneously).

The AND option should be used for detection of free fall with all Lo axes checked (xLo, yLo, zLo)

and Trigger Level set to 0.5g or less (8% for 24g accelerometer with Range = 6g).

xHi, yHi, zHi- checking one or more of these boxes will trigger a data acquisition when the magnitude

of the acceleration along any of the checked axes exceeds the value in Trigger Level if AND box is not

checked.

If AND is checked, the magnitude of acceleration along all checked axes must exceed Trigger Level

before an acquisition is triggered.

Rev1.3 42

xLo, yLo, zLo- checking one or more of these boxes will trigger a data acquisition when the

magnitude of the acceleration along any of the checked axes is less than the value in Trigger Level if

AND box is not checked.

If AND is checked, the magnitude of acceleration along all checked axes must be less than Trigger

Level before an acquisition is triggered.

The AND option should be used for detection of free fall with all Lo axes checked (xLo, yLo, zLo)

and Trigger Level set to 0.5g or less (8% for 24g accelerometer with Range = 6g).

Trigger Level(%of Range)- This control sets the level of acceleration that will initiate the start of a

data acquisition for Waveform on Trigger or Peak Detect on Trig. The Trigger Level is a percentage of

the range specified in the Range box. For example, If the Range button checked is 12g and Trigger

Level(%of Range) is 25, Trigger Level in g is 3g (1g = 9.8m/s^2).

Offset(mg), Scale(mg)- The values in these boxes are calibration constants for your accelerometer.

Because of variability in manufacture, every accelerometer has a unique set of calibration constants. The

Fremont USB Instrument Driver software can determine these calibration constants for you (see

Accelerometer Calibration below). The unit of these constants is in mg, 1/1000 of the acceleration due to

gravity in m/s2, where g = 9.8m/s2. Offset is the number that needs to be added to the accelerometer

reading to set the reading to zero when no acceleration is applied. Scale is the number the accelerometer

reading must be multiplied by to read 1g.

Accelerometer Calibration- Press this button to start calibration of your accelerometer. The specified

axis of the accelerometer must be properly aligned to gravity. We recommend you mount the

accelerometer temporarily on a block or piece of channel material with right angle sides for calibration,

shown in Fig. AC7.

During Accelerometer Calibration you will be prompted to align the accelerometer with each of its

primary axes parallel to gravity for 3s for each axis. Each axis requires 6 seconds for data acquisition, 3s

for the positive direction and 3s for the negative direction. You will be prompted when data acquisition

has been completed along an axis to change the orientation of the device to the next orientation. A graphic

in the software will indicate proper orientation for each axis. The graphic is a representation of the

accelerometer board, showing the accelerometer chip and the FFC connection for X and Y calibration and

a cross section of the board for Z calibration (chip up for +Z). See Fig. AC7.

Fig. AC7. Accelerometer mounted on channel for calibration. Orientations of channel shown is for +Z

axis and +X axis. Graphic displayed in software during calibration for these axes is also shown.

Rev1.3 43

After the accelerometer has been aligned relative to the direction of gravity as indicated by the graphic,

click CONTINUE. If you wish to discontinue calibration before completion, click EXIT to quit

Accelerometer Calibration.

When data acquisition is complete new values will be entered in Offset(mg) and Scale(mg). A value of

zero in any box in Scale(mg) indicates improper alignment of the accelerometer during Accelerometer

Calibration and calibration should be run again.

Confirm these values for various alignments of the accelerometer and if the values are appropriate save

with Save/Open Config.

Accelerometer Calibration values must be saved with "Save as..." in Save/Open Config or values will be

lost. To save these values as the default configuration which is loaded when the program starts, save the

file as "Acc8g_0" for 8g accelerometers, as "Acc24g_0" for 24g accelerometers, or as "Acc400g_0" for

400g accelerometers in Save/Open Config "Save as..." file dialog.

Calibration values for an accelerometer may differ for the range selected. Calibration for each range

should be run and a unique configuration file should be created for each range. For example, if a 24g

accelerometer is attached, run individual calibrations for the 6g, 12g, and 24g ranges. Save each range

with a unique file name and load this configuration when you use the range.

If you exit calibration before it completes, Offset(mg) and Scale(mg) values will be incorrect. The easiest

way to recover the previous values is by closing the USBID Instrument Driver software and restarting the

software. Alternatively, you can open the default configuration with the Save/Open Config box for the

configuration of your accelerometer ("Acc24g_0" for 24g accelerometers or "Acc400g_0" for 400g

accelerometers). If you have accidentally overwritten the default configuration (either "Acc24g_0" or

"Acc400g_0") just open the C:\Fremont\Config file and delete the bad file. Then close the USBID

Instrument Driver software and restart the software. The default configuration will be loaded and you can

rerun Acceleration Calibration.

Read Acceleration- When the Read Value button is pressed in this box, the current values of X, Y, Z,

and Magnitude of acceleration are read.

Save/Open Config Box This box is used to open or save a custom configuration. When the software is started with an attached


accelerometers this will be either Acc24g_0.csv or Acc400g_0.csv. When a configuration is saved all

values that can be modified will be saved. This includes all boxes and radio buttons checked, and values

in numeric entry boxes.




configuration as Acc24g_0.csv or Acc400g_0.csv, depending on the type of accelerometer.


and delete the appropriate file, either Acc24g_0.csv or Acc400g_0.csv. When the Fremont software is

restarted the default configuration will be recreated in c:\Fremont\Config and the default values loaded.

Rev1.3 44

Note: Do not modify a configuration file in a text editor. Format of the file will be changed and cannot be

read by the Fremont software. Make all changes to a configuration in the Fremont software and save

changes to a configuration file with the Save/Open Config box.

Accelerometer Acq Box This box is located to the right of the plot area. The buttons in this box set the type of acquisition.

START- Pressing this button will start an acquisition. Depending on the type of acquisition selected

below the START button, the text on the button will change to either STOP or Acq WF in Progress.

STOP is shown when the acquisition type selected is Real Time, Peak Detect on Trig or Waveform on

Trigger. To end an acquisition, press the STOP button.

Acq WF in Progress is shown when the acquisition type selected is Acquire Waveform. Acq WF in

Progress indicates that the acquisition is being handled by the USBID and the PC program is waiting for

the USBID to indicate that the acquisition is complete. When an acquisition has been completed the

button text will change back to START.

While a waveform is being acquired or a scan of samples is being made for a peak detect, the green LED

on the USBID board will be on.

Plot Length(S)/WF Length(S)/Scan Length(S)/Plot Length(Pts)- The function of this control depends

on the type of acquisition chosen with the buttons in Accelerometer Acq.

For Real Time the text for this control is Plot Length(S) and it sets the number of samples plotted in the

chart before the chart retraces, also the number of samples that can be saved, maximum value is 300.

For Acquire Waveform and Waveform on Trig the text for this control is WF Length(S) and this control

sets the number of samples acquired in the waveform, the number of samples plotted, and the number of

samples that can be saved, maximum value is 300.

For Statistics the text for this control is Plot Length(Pts) and it sets the number of samples plotted in the

chart before the chart retraces.

For Peak Detect on Trig the text for this control is Scan Length(S) and this control sets the number of

samples scanned for a peak value, maximum value is 65535. The number of samples plotted and number

of samples that can be saved are set with No. of Peaks to Acquire (see Peak Detect on Trig below).

Real Time- When this button is checked data is acquired and displayed in the plot area at a data rate of 20

to 30 S/s. Set Data Rate(S/s) to 50 or above. Lower values can be used but with lower values there will be

multiple reads of the same value. Press the STOP button to stop acquisition. Data can be saved with Save

Current Data.

Acquire Waveform- When this button is checked X,Y,Z and Magnitude waveforms will be acquired

with the length in samples of the waveforms specified in the WF Length(S) control. Save data acquired

with Save Current Data button.

Rev1.3 45

Waveform on Trigger- When this button is checked a waveform will be acquired when a trigger occurs

based on the parameters set in the Trigger Box, described above. Save data acquired with Save Current

Data button.

An acquisition can be stopped by pressing the STOP button if a waveform acquisition is not in progress.

If a waveform acquisition is in progress, the green LED on the USBID will be constantly lit (not

blinking). Pressing the STOP button while an acquisition is in progress will initiate the start of a new

acquisition after the current acquisition has completed.

Statistics- When this button is checked statistics for all three axes will be collected periodically. The

statistics option is a powerful means to sample a large amount of data and get an overall view of the data

sampled. The number of samples monitored for statistics is specified in the Samples/Pt control. For each

axes the maximum, minimum, mean, and standard deviation will be reported for the number of samples

set in the Samples/Pt control. The maximum magnitude of the acceleration is also reported

(X2+Y2+Z2)^1/2 for the number of samples set. The time between points is set with the Time(s)/Pt control.

The time between points is the time in seconds between points. As an example, if Samples/Pt =300, Data

Rate(S/s)=400, and Time(s)/Pt=1.0, once per second 300 samples will be measured for statistics at 400

samples/second. Data will be measured for 300/400 seconds at a 1 second interval.

Log Data to PC- when this box is checked data will be automatically logged to the hard drive of

your PC, allowing an infinite number of points to be collected. The file location is displayed in the

text box next to the Save Current Data button.

Samples/Pt- This control sets the number of samples measured to calculate a single statistic point.

One statistic point will include maximum, minimum, mean, and standard deviation for all axes (X,

Y, Z) for the number of samples. The values in the point also include maximum acceleration

magnitude during the sample period and time of start of acquisition of samples. Maximum number

of Samples/Pt is 300.

Time(s)/Pt- This control sets the time period in seconds between points. The value entered in this

control is coerced by the value entered in Samples/Pt control and Data Rate(S/s). As an example,

if Samples/Pt is 200, Data Rate(S/s) is 100, and Time(s)/Pt is 1, the time between points will be

greater then 2 seconds. This is because (200Samples/Pt) / (100Samples/s) = 2s/Pt, greater then

Time(s)/Pt.

Point No.- This text box displays the number of points that have been saved to the PC when the

Log Data to PC box is checked. If the Log Data to PC box is checked, the file these points are

saved to is shown in the text box to the right of the Save Current Data button.

Peak Detect on Trig When this button is checked the USBID will monitor the accelerometer until a

trigger occurs based on the parameters set in the Trigger Box, described above. When a trigger occurs the

USBID will scan the number of samples entered in Scan Length(S) for the maximum absolute value

found for any axis, X, Y, or Z. The peak value reported in the data file will be the maximum absolute

value found for the X, Y, or Z axis. The values reported for the other axes will be the value of the axis at

the time the maximum is detected. The USBID will then scan for subsequent peaks based on trigger

values and number of peaks to detect entered in Pks to Detect control.

Rev1.3 46

No of Peaks to Acquire control specifies the number of peaks to acquire before the acquisition is

stopped, maximum value is 190. This is also the number of samples that will be plotted in the plot area.

When all peaks are acquired the text on the START/STOP button will return to START and all

disabled buttons and controls will be enabled.

Check Pk Status button can be used to determine how many peaks have been acquired. When this

button is pressed all peaks that have been acquired will be plotted. This button is only enabled after the

start of a Peak Detect on Trig acquisition.

Do not press the STOP button to check the number of peaks detected. If STOP is pressed, the

acquisition is ended.

The text on the START/STOP button will remain STOP even after all peaks are acquired. Press the

Check Pk Status to check acquisition progress. If all peaks have been acquired, the text on the

START/STOP button will change from STOP to START, all disabled buttons and controls will be

enabled and all peaks will be plotted.

To discontinue an acquisition before all peaks are acquired press the STOP button. The text on the

START/STOP button will change from STOP to START, all disabled buttons and controls will be

enabled, and all peaks acquired will be plotted.

Plotted data can be saved at any time with the Save Current Data button.

Save Current Data- When this button is pressed data shown in the plot area is saved. A Save window

appears and data can be saved to either the default location/file name or a user specified location/file

name. The default location for data saved is to the folder c:\Fremont\Data with a date/time string as the

file name. The file name is the date and time when the measurement is saved (PC system time). For

example, the file name 20170515125604.csv indicates that the acquisition was saved in 2017(year) in



The formatting of the saved data is similar for Real Time, Acquire Waveform, Waveform on Trigger, and

Peak Detect on Trig acquisitions. An example of a saved file for these acquisition types is shown in Fig.

AC8. Saved Statistics data has a different format, described below.

n Time(s) Xaccel(g) Yaccel(g) Zaccel(g) Magnitude(g)AcqType:PkDetectOnTrig SamplesScanned:100 DataRate(S/s):400 gRange:6 Threshold:50

0 247.6382 1.5719 0.184 -4.9033 5.1524

1 257.9829 2.3653 -4.1568 2.0382 5.1988

2 261.9466 2.3542 4.678 2.314 5.7254

3 265.1377 1.1269 3.502 -1.7581 4.0773

4 267.6958 0.8435 3.043 -2.0573 3.7688 Fig. AC8. Saved data file example for Peak Detect on Trig.

The values shown in these columns are described below:

n- This value will be the sample number for a waveform while using Real Time, Waveform, or

Waveform on Trigger. For Peak Detect on Trigger, this value will be the number of the peak detected.

Time(s)- This value is the time at acquisition for a sample. Reported time values are measured using a

high accuracy timing circuit on the USBID. The default start value is the number of seconds from

when the USBID is first connected to a USB port.

Rev1.3 47

Time(s) can be set to the current time on your PC or to zero with a function on the Setup tab. Another

function on the Setup tab can be used to convert the Time(s) column of a saved file to an expanded file

format containing three additional columns: yr/month/day; hr/min/s; and ms. See Description of Setup

Tab Controls to set time on the USBID and convert the Time(s) column of a saved file to date/time

format.

Real Time- A single sample is acquired by the USBID and transmitted to the USBID software on

your PC. Because of variability in how often the USB connection is polled for updated information,

the time between samples can vary.

Waveform or Waveform on Trigger- The value is the time at acquisition for the sample. The time

between samples may differ from the data rate that was checked in Data Rate(S/s). This is because

samples are acquired at a rate set by the accelerometer integrated circuit. This rate uses a low

accuracy timer resident on the accelerometer integrated circuit. The value reported in Time(s) uses

the high accuracy timing circuit on the USBID and can differ substantially from the rate that is

checked in Data Rate(S/s).

Peak Detect on Trigger- The value is the time at the peak value measured using the USBID timing

circuit.

Xaccel(g), Yaccel(g), Zaccel(g), Magnitude(g)- These columns are the measured acceleration values.

X, Y, and Z are acceleration along the corresponding axes and Magnitude = (Xaccel2 + Yaccel2 +

Zaccel2)1/2.

To the right of the data columns in all saved data files is a header showing acquisition parameters.

The location of the saved file is shown in the text box labeled Data File. On the start of a new

acquisition the text in this box is cleared. This is to indicate to the user that the new data currently

displayed in the plot area has not been saved.

Statistics Data Save- When Statistics data is saved either with Save Current Data or by checking the “log

data to PC” check box, the data saved will be in the format shown below in Fig. AC8a. The first column

will be the point number. The second column will be the time at which the acquisition of this point was

started. The third column is a calculation of the actual Data Rate(S/s), using the start time of the

acquisition and end time of the acquisition. The next 12 columns contain the maximum, minimum, mean,

and standard deviation of the point for each axis. The final column is the maximum acceleration

magnitude (max of acceleration(X2+Y2+Z2)1/2).

n Time(s) DataRate(Hz)Xmax(g) Xmin(g) Xmean(g) XstDev(g) Ymax(g) Ymin(g) Ymean(g) YstDev(g) Zmax(g) Zmin(g) Zmean(g) ZstDev(g) MaxAccelerationMagnitude(g)

0 3989.377 398.1816 0.0626 -0.0963 -0.023857 0.049034 0.038 -0.0098 0.014317 0.013453 4.8133 -2.5227 0.816294 2.521956 4.8139

1 3989.574 395.4959 0.0538 -0.0932 -0.029063 0.045096 0.047 -0.0218 0.013986 0.016668 4.3561 -2.3586 1.178551 2.344676 4.3566

2 3989.782 395.4959 0.0685 -0.0845 -0.017217 0.040783 0.056 -0.0098 0.015523 0.016569 3.978 -2.2208 0.838234 2.196966 3.9784

3 3990.031 400.7597 0.0508 -0.0727 -0.017369 0.037515 0.029 -0.0128 0.008434 0.01316 3.7875 -1.8837 0.84804 2.027598 3.7877

4 3990.256 398.1816 0.0449 -0.0727 -0.017911 0.0325 0.044 -0.0158 0.014834 0.013189 3.6497 -1.6082 1.061474 1.82315 3.6503

5 3990.498 395.6364 0.0479 -0.0609 -0.016431 0.031743 0.044 -0.0128 0.013726 0.013364 3.4563 -1.4294 1.092291 1.728725 3.4567

6 3990.756 395.4959 0.0391 -0.0432 -0.012549 0.02833 0.038 -0.0218 0.012271 0.014701 3.2804 -1.277 0.996643 1.555421 3.2808

7 3990.938 402.9338 0.0479 -0.0462 -0.006997 0.027392 0.044 -0.0098 0.014574 0.012117 3.128 -1.1686 0.881354 1.535266 3.1283

8 3991.19 398.1816 0.0538 -0.0491 -0.007526 0.02624 0.032 -0.0098 0.014569 0.009309 3.0225 -0.9957 0.88612 1.450436 3.0227

9 3991.409 403.2255 0.042 -0.0432 -0.00792 0.023506 0.047 -0.0098 0.014154 0.011801 2.8788 -0.8843 1.063466 1.329108 2.8791 Fig. AC8a. Saved data file example for a Statistics acquisition.

To the right of the data will be a header containing the acquisition parameters, shown below in Fig. AC8b.

Rev1.3 48

AcqType:Statistics Samples/Pt:35 SampleRate(S/s):400 gRange:6 Fig. AC8b. Saved acquisition parameters for a Statistics acquisition.

Rev1.3 49

Advanced Acquisition Controls

When this button is clicked, a window is opened allowing the acquisition of periodic waveforms, multiple

waveforms on trigger, or up to 10900 peaks on trigger. Advanced Acquisition features allow periodic

sampling of accelerometer data by setting the period between waveforms (for Periodic Waveform) or by

using Masking (for Waveform on Trigger or Peak Detect on Trigger). Screenshots for Advanced

Acquisition Controls are shown at the end of this section.

Acquisition Type and Values box is used to set the type of acquisition and some of the values associated

with the acquisition type.

Periodic Waveform- When this button is checked the USBID will acquire waveforms periodically. The

period between waveforms is set in the Waveform Period box. The number of waveforms acquired is set

with the No.of Waveforms control. The number of samples in the waveform is set with WF Length(S)

control. The maximum total number of samples acquired for all waveforms is approximately 10,000. The

value in WF Length(S) is coerced by the value in No. of Waveforms such that

(No.ofWaveforms+12)*(WF Length(S))10912

The start time of the first waveform acquired will always be an integer second value.

Waveform Period box sets the period between waveforms. Period is the time (or samples) from the

start of a waveform acquisition until the start of the next waveform acquisition. The period between

waveforms can be specified as either Samples or Seconds.

The values in these two controls must be greater than the value shown in the boxes labeled Minimum.

Seconds- When this button is checked the period between waveforms is set in seconds. Resolution

is 1 second. Waveforms with this option will always start on an integer value of seconds measured

by the USBID. The value in the Seconds control must be greater than the value shown in the box to

the right labeled Minimum. When the value in the Seconds control is less than the minimum

allowed value, the value in the Seconds control will be red. If an acquisition is started with the

Seconds value less than the minimum allowed value, the Seconds period will be coerced to the

minimum allowed value when an acquisition is started.

Samples- When this button is checked the period between waveforms is set in samples. This option

should be used when you want the time between waveforms to be less than 1 second or not an

integer multiple of seconds. The value in the Samples control must be greater than the value shown

in the box to the right labeled Minimum. When the value in the Samples control is less than the

minimum allowed value, the value in the Samples control will be red. If an acquisition is started

with the Samples value less than the minimum allowed value, the Samples period will be coerced to

the minimum allowed value when an acquisition is started. The period set uses the low accuracy

timer on the accelerometer chip. Timing using this option is good for sample rates of 2S/s-400S/s.

For 1S/s or 1000S/s, actual data rate may differ by as much as 40%.

All time data saved uses the high accuracy timer on the USBID and not the nominal sample rate

specified in the Data Rate(S/s) box.

Rev1.3 50

Waveform on Trigger- When this button is checked the USBID will monitor the accelerometer until a

trigger occurs (trigger level set in Trigger Level(%of Range)). When a trigger occurs the USBID will

acquire a waveform. The number of waveforms acquired is set with the No.of Waveforms control. The

number of samples in the waveform is set with WF Length(S) control. The maximum total number of

samples acquired for all waveforms is approximately 10,000. The value in WF Length(S) is coerced by

the value in No. of Waveforms such that

(No.ofWaveforms+12)*(WF Length(S))10912

The start time of the first waveform acquired will always be an integer second value.

Masking is available for Waveform on Trigger. Masking can be used to delay the start of a waveform

acquisition after a trigger (Post Trigger Mask) or it can be used as a delay time before the trigger is

enabled after a waveform acquisition (Post Waveform Mask) for periodic sampling of data. These options

can be used individually or in combination.

Peak Detect on Trigger-When this button is checked the USBID will monitor the accelerometer until a

trigger occurs (trigger level set in Trigger Level(%of Range)). When a trigger occurs the USBID will scan

the number of samples entered in Scan Length(S) for the maximum absolute value found for any axis, X,

Y, or Z. The peak value reported in the data file will be the maximum absolute value found for the X, Y,

or Z axis. The values reported for the other axes will be the value of the axis at the time the maximum is

detected. The time value in a saved data file is the time measured by the USBID when the peak occurred.

The USBID will then scan for subsequent peaks based on trigger value and number of peaks to detect

entered in Pks to Acquire control.

Masking is available for Peak Detect on Trigger. Masking can be used to delay the start of a peak

acquisition after a trigger (Post Trigger Mask) or it can be used as a delay time before the trigger is

enabled after a peak acquisition (Post Waveform Mask) for periodic sampling of data. These options can

be used individually or in combination.

Minimum Time For Acquisition(s) text box indicates the minimum time it will take for all waveforms

and peaks to be acquired in seconds. This value is calculated using the values entered in the Acquisition

Type and Values box.

Start Acquisition button is used to start an acquisition. When this button is pressed an acquisition is

started and the text of the button will change to Pause/Check Acquisition. After the Start Acquisition

button is pressed all controls will be disabled except the Pause/Check Acquisition button. Pressing this

button also clears all data from previous acquisitions.

Pause/Check Acquisition button when pressed will tell you the current status of the acquisition. The

USBID software does not poll the USBID to check acquisition status. The text on this will remain

Pause/Check Acquisition Status even if the acquisition is complete. This button must be pressed to poll

the USBID to check status. When this button is pressed the number of waveforms or peaks that have

been acquired will be shown in a text box labeled either No. of Waveforms Acquired or No. of Peaks

Acquired, depending on acquisition type.

If the number of waveforms or peaks acquired is less than the value in the No. of Waveforms or Pks. to

Acquire box, the Pause/Check Acquisition button is replaced with two buttons. These two buttons are

Restart Acq and End Acq.

Rev1.3 51

The Download and Save Data button is also enabled. With this option, you can save the data already

acquired.

If the number of waveforms or peaks acquired is equal to the value in the No. of Waveforms or Pks. to

Acquire box, the Pause/Check Acquisition button is replaced with the Start Acquisition button.

Restart Acq button will restart the acquisition and the Pause/Check Acquisition button will be visible.

When an acquisition is restarted using the Restart Acq button, subsequent data from waveforms or

peaks will be appended to an existing data file on the USBID.

End Acq button will end the acquisition and the Start Acquisition button will be visible. All controls

will also be enabled.

If you wish to save the data acquired use the Download and Save Data button. Save data before

changing the values in any controls. Saved data uses displayed control values and will be incorrect if

the values are changed from the values used during the acquisition.

Download and Save Data button is used to save data to the hard drive. The number of waveforms or

peaks saved is shown in the No. of Waveforms Acquired/No. of Peaks Acquired text box. Data saved is

all current data for the acquisition. Data can be saved whenever an acquisition is paused or at the end of

an acquisition (all waveforms or peaks acquired). When an acquisition is restarted using the Restart Acq

button, subsequent data from waveforms or peaks will be appended to an existing data file on the USBID.

Later saves of data will contain all data from previous data saves with new data appended.

The default location for data saved is to the folder c:\Fremont\Data with a date/time string as the file

name. The file name is the date and time of the start of the measurement (PC system time). For example,

the file name 20170515125604.csv indicates that the acquisition started in 2017(year) in 05(month, May)

on 15(day) at 12(hour) 56(minute) 04(seconds). The file format is CSV, Comma Separated Values,

readable by most spreadsheets.

When a data acquisition is completed, indicated by the text of the Pause/Check Acquisition changing to

Start Acquisition when the button is pressed, all controls are enabled but data must be saved before values

in controls are changed. Saved data uses displayed control values and will be incorrect if the values are

changed from the values used during the acquisition.

Saved data is similar to that described above for Save Current Data. The primary differences are that an

additional column is added indicating waveform number(for Periodic Waveform or Waveform on

Trigger) and the header can have additional information concerning waveform period or masking values.

An example of saved data is shown in Fig. AC 9.

n Time(s) WaveFormXaccel(g) Yaccel(g) Zaccel(g) Magnitude(g)AcqType:WFonTrigger WaveformLength(S):200 DataRate(S/s):100 gRange:6 Threshold:20 PostTrigMask(Samples):100 PostWFmask(Samples):150

0 851.9876 0 0.0323 -0.0137 -0.9938 0.9944

1 851.9975 0 0.0116 -0.0227 -0.9968 0.9971

2 852.0075 0 0.0294 -0.0167 -1.0466 1.0471

3 852.0175 0 0.0087 -0.0137 -0.9997 0.9998

4 852.0274 0 0.0087 -0.0137 -0.9938 0.994 Fig. AC9. Saved data file example for Waveform on Trig during Advanced Acquisition.

Masking Box

Masking is used to impose delays in data acquisition for Waveform on Trigger or Peak Detect on Trigger.

This is useful for periodically sampling data. Two types of delay are available: Post Trigger Mask and

Post Waveform Mask. These delays can be used separately or in combination. To use masking, the

Rev1.3 52

masking check box must be checked as well as at least one of the check boxes specifying type (Post

Trigger Mask or Post Waveform Mask).

Post Trigger Mask will impose a delay after a trigger. When a trigger occurs, data acquisition will

begin after the period specified as either samples or seconds.

Post Waveform Mask will impose a delay after a waveform has been acquired. During this delay the

trigger is disabled. At the end of the delay the trigger is enabled. The delay can be specified as either

Samples or Seconds.

For Post Trigger Mask and Post Waveform Mask, two masking options are available: Samples or

Seconds.

Seconds

For Post Trigger Mask, current seconds is read at the time of the trigger and added to the value entered

in the Seconds box. When the measured seconds value exceeds this sum, waveform acquisition begins.

Resolution is 1 second. Waveforms with this option will always start on an integer value of seconds

measured by the USBID.

For Post Waveform Mask, current seconds is read at the time of the waveform and added to the value

entered in the Seconds box. The trigger is then disabled until the measured seconds value exceeds this

sum. Resolution is 1 second.

Samples

This option should be used when you want a masking value of less than 1 second or not an integer

multiple of seconds. Samples masking uses the rate checked in the Data Rate(S/s) box for timing. This

rate is also the rate a waveform is acquired. The sample rate uses the low accuracy timer on the

accelerometer chip. Timing using this option is good for sample rates of 2S/s-400S/s. For 1S/s or

1000S/s, actual data rate may differ by as much as 40%.

For Post Trigger Mask, after a trigger, data is read (but not saved) from the accelerometer at the rate

checked in the Data Rate(S/s) for the number of samples entered in the Samples mask box. A

waveform is then acquired at the specified data rate and saved.

For Post Waveform Mask, after a waveform is acquired, data is read (but not saved) from the

accelerometer at the rate checked in the Data Rate(S/s) for the number of samples entered in the

Samples mask box. The trigger is then enabled.

All time data saved uses the high accuracy timer on the USBID and not the nominal sample rate specified

in the Data Rate(S/s) box.

Rev1.3 53

Screenshots The figures below show what you will see in an Advanced Acquisition.

Fig. AC10. Periodic Waveform before an acquisition is started.

Fig. AC11. Waveform on Trigger before an acquisition is started. Masking is enabled.

Rev1.3 54

Fig. AC12. Peak Detect on Trigger before an acquisition is started. Masking is enabled.

Examples below use a Periodic Waveform acquisition but will be similar for other types.

Fig. AC13. Waveform on Trigger after an acquisition is started.

Rev1.3 55

Fig. AC14. Waveform on Trigger when acquisition is paused.

Fig. AC15. Waveform on Trigger when acquisition is paused and data saved.

Rev1.3 56

Setup Tab Controls

The available controls in the setup tab are used to set the clock on the USBID and to convert the Time(s)

column in a saved data file to date/time format. The available controls on the setup tab are shown in Fig.

AC16.

Fig. AC16. Setup Tab Controls.

Set USBID Time Box





time.






Use System Time When this radio button is checked and the Set button is pressed, the current PC

system time is read and the real time clock on the USBID is set to this value. In saved data the

Time(s) value will be the current number of seconds from 2000, January 1, 00:00:00 (assuming

the time on the system clock is correctly set).






checked.






only.

Rev1.3 57

The figure below (Fig. AC17) shows the result when the button Use System Time is checked, the


When the Set button is pressed, the current system time on the PC is read and used to set the clock

on the USBID.



Fig. AC17. Set USBID time to system time and then read.


Fig. AC18. Control box to convert the time column in a saved file to Date/Time format.




or a Custom value.





To convert a file:






Rev1.3 58





showing the file opened and the new file to which data has been saved. This is shown in Fig. AC19.

Fig. AC19. Control box after a date/time conversion.


and appended to new file containing all of the original data is shown below in Fig. AC20.

Fig. AC20. Time in seconds converted to date and time format.

Notes:




will occur.

n Time(s) Xaccel(g) Yaccel(g) Zaccel(g) Magnitude(g)

0 5.52E+08 0.4226 -0.0507 0.4958 0.6534

1 5.52E+08 0.4696 -0.1017 0.4606 0.6656

2 5.52E+08 0.5256 -0.1017 0.4078 0.673

3 5.52E+08 0.5875 -0.1076 0.3727 0.704

n m/d/yr hr:min:s ms Time(s) Xaccel(g) Yaccel(g) Zaccel(g) Magnitude(g)

0 6/27/2017 22:55:53 757.4461 5.52E+08 0.4226 -0.0507 0.4958 0.6534

1 6/27/2017 22:55:53 767.405 5.52E+08 0.4696 -0.1017 0.4606 0.6656

2 6/27/2017 22:55:53 777.3629 5.52E+08 0.5256 -0.1017 0.4078 0.673

3 6/27/2017 22:55:53 787.322 5.52E+08 0.5875 -0.1076 0.3727 0.704

Rev1.3 59

Examples

All examples are for a 24g accelerometer. The first examples shown are for a 24g accelerometer mounted

on the end of a cantilever beam. The beam is aluminum, 440mm long, 19mm wide, and 3mm thick. The

waveform produced is a damped harmonic oscillator. The accelerometer is mounted on the cantilever

beam such that the z-axis of the accelerometer is parallel to the acceleration due to gravity (acceleration

measured on the z-axis will be 1g when the cantilever beam is at rest). This is shown below in Fig. AC21.

Fig. AC21. Accelerometer mounted on cantilever beam.

The final examples are for Waveform on Trigger where the trigger is due to free fall or shock.

440 mm

3 mm

Accelerometer

Rev1.3 60

Example1 For the example shown in Fig. AC22, the cantilever beam is plucked with Trigger parameters

Trigger Level = 20%, and OR logic for checked boxes (xHi, yHi, zHi). For the Range selected, 6g, a

trigger will occur initiating a waveform acquisition when the absolute value of acceleration exceeds 1.2g

(6g*0.2) on any of the checked axes (an acceleration of -1.2g would also cause a trigger). In this example,

the START button was pressed when the acceleration along the z-axis was below 1.2g so the acquisition

began when the z-axis acceleration exceeded 1.2g and rising.

Fig. AC22. Waveform on Trigger for an accelerometer mounted to a cantilever beam.

Rev1.3 61

Example2 The example below, Fig AC23, uses the same trigger parameters and Range as that in Fig.

AC22, but the START button was pressed when the magnitude of the acceleration along the z-axis was

greater than 1.2g but falling. A trigger will occur whenever the trigger condition is met, set in the Trigger

box.

Fig. AC23. Waveform on Trigger for an accelerometer mounted to a cantilever beam.

Rev1.3 62

The next 4 examples are for Peak Detect on Trig and capture the peak values of acceleration in the

sinusoidal waveforms shown above. The accelerometer in these examples is mounted to the cantilever

beam described above. The first two examples use different trigger parameters to capture the same data.

The next two examples show the use of the Check Pk Status button.

Example3 The first Peak Detect on Trig example, Fig. AC24, uses the same trigger parameters used in

the above two examples: the AND box is not checked; xHi, yHi, and zHi are checked; Trigger Level is

20% of Range (6g*0.20 = 1.2g). When the beam is plucked, this will produce a trigger whenever the

absolute value of acceleration along any of the axes exceeds 1.2g. The period in samples of the sinusoidal

waveform at 400S/s is ~33 Samples so Scan Length(S) is set to 30. For a periodic waveform, Scan Length

should be slightly less than the period of waveform otherwise peaks could be missed.

Fig. AC24. Peak Detect on Trig for an accelerometer mounted to a cantilever beam using acceleration

greater than Trigger Level to trigger the start of a scan of a waveform for a peak.

Rev1.3 63

Example4 The next example produces the same data output as the preceding example but uses very

different trigger parameters. In Fig. AC25, Peak Detect on Trig monitors a single axis for the trigger, zLo.

When the beam is plucked, with a Trigger Level of 12%, a waveform will be scanned for a peak when the

magnitude of the acceleration along the z axis is less the 0.72g(0.12*6g). The number of samples scanned

for a peak is 30.

Fig. AC25. Peak Detect on Trig for an accelerometer mounted to a cantilever beam using acceleration less

than Trigger Level to trigger the start of a scan of a waveform for a peak.

Rev1.3 64

The next 2 examples show the use of the Check Pk Status button. Trigger parameters are the same as

those used in Fig. AC24.

Example5 In Fig. AC26, the cantilever beam has been plucked, the acquisition started, and the Check Pk

Status button has been pressed. When the Check Pk Status button is pressed, the acquisition is paused,

data is downloaded, and then the acquisition is restarted. The plotted data shows 23 peak values have been

measured.

Fig. AC26. Peak Detect on Trig plot when the Check Pk Status button is pressed.

Rev1.3 65

Example6 This example shows data acquired when a peak detect measurement is stopped and then

restarted. During the pause, while data is being downloaded, several hundred milliseconds of data can be

missed. This is the cause of the discontinuity (Fig. AC27 below) in data of the completed acquisition

when plotted as a function of point number, Time values will be correctly reported. When peak values are

plotted as function of time there will be a gap in time but no discontinuity in slope of the peak values.

Fig. AC27. Peak Detect on Trig plot when data acquisition is complete, when the Check Pk Status button

is pressed during acquisition.

Rev1.3 66

Example7 This example shows a Statistics data acquisition. In Fig. AC28, the cantilever beam has been

plucked, the acquisition started, and then stopped when the acquisition reachs 100 points. Data Rate is set

to 400S/s, the same as in the examples above. From Example 2 you can see that the period of the

waveform is approximately 33 Samples at this Data Rate. Samples/Pt is set at 35 Samples/Pt so that

during the acquisition of a point one of the samples will be a maximum value of the periodic waveform.

Time(s)/Pt has been set at the minimum value of 0.1. The plotted value is Max. Trigger is not used in

Statistics acquisitions.

Fig. AC28. Statistics acquisition example for the accelerometer mounted to the cantilever beam.

The rate of decay of the oscillation is much faster in terms of point number compared to the previous

examples. Peaks are missed in this example because raw data is transferred to the PC and then parsed for

the statistic values. In the saved data file the time value of the start of acquisition is saved for each point.

When max value shown in the plot above is plotted in comparison to the data from Fig. AC24 in terms of

time, the data sets from Fig. AC28 and Fig. AC24 are shown to be identical. This is shown in Fig. AC29

below.

Rev1.3 67

Figure AC29 shows a comparison of the data from a Statistics acquisition (Fig. AC28) with that from a

Peak Detect on Trig acquisition (Fig. AC24). When plotted in terms of time the data sets are identical.

Comparison of Pk Detect with Statistics Measurement

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10

Time(s)

Ma

xim

um

Acce

lera

tio

n(g

)

Statistics

Pk Detect

Fig. AC29. Comparison of Peak Detect on Trig acquisition with Statistics acquisition.

Rev1.3 68

The next 2 examples show similar shock events captured after free fall.

Example7 In the first of these examples, shown in Figure AC30, trigger parameters are set so that the

waveform acquisition begins when the acceleration along any axis exceeds 1.2g (AND box not checked,

Range is set to 6g, Trigger Level%=20, so 6g*0.20=1.2g).

Fig. AC30. Waveform on Trigger when triggered by Trigger Level on any axis exceeding 1.2g.

Rev1.3 69

Example8 Fig. AC31 is triggered by freefall. In Trigger parameters, AND box is checked and xLo, yLo,

and zLo are also checked, requiring the magnitude along all axes to be less than 0.48g (6g*0.08) for a

trigger. This will capture the entire shock event.

Fig. AC31. Waveform on Trigger when triggered by Trigger Level on all axes less than 0.48g, indicating

free fall.

Rev1.3 70

Specifications


Accelerometer Instrument

Mass: 0.67g

USBID

Mass: 2.35g


0.75 (12.7)

1.00 (25.4)

0.125 (3.17)

.080 (20.32)

0.125 (3.17)

(10.

16)

0.64 (16.26)

0.40 (10.2)

Rev1.3 71

5. 2 Channel Strain Gauge/ Differential Amplifier

The Strain Gauge Instrument is a two channel differential amplifier that can be used to acquire data for

full bridge strain gauge circuits or other applications requiring a high gain differential amplifier.

• Acquires data for 2 full bridge strain gauge circuits simultaneously or 2 channels differential.

• Acquisition rates from 1S/s to 10,000S/s.

• 12 bit resolution.

• Low pass filtering in software by averaging data.

• Balance is set independently for each channel on the board with multi-turn potentiometers.

• Triggers can be used to initiate an acquisition.

o Trigger can be set to either channel or both.

o Trigger level and trigger on rising or falling edge set in software.


o Real Time- Continuous acquisition of data at ~30S/s.

o Window- One shot data acquisition of up to 1000 points at up to 10kPts/s.

o Window On Trigger- One shot data acquisition of up to 1000 points when trigger

conditions are met at up to 10kPts/s.

o Peak Detect on Trigger- Detect the peak (or minimum) value after a trigger event for one

or both channels. Scan length for peak, number of peaks to detect, and trigger level and

type set in software.

o Statistics - Continuous acquisition of maximum, minimum, average, and standard

deviation for one or both channels. Scan length for statistics and acquisition rate are set in

software.

▪ Acquired statistics can be automatically saved to a PC file for unlimited data

acquisition length.

• Adjustable gain. Gain as supplied is 505 but can be reduced with external resistors.

o Gain can be set from 5 to 505 with external resistors.

• 3.3 V strain gauge excitation is supplied by the board. An external excitation can also be used.

• High accuracy voltage reference on USBID provides 0.04% accuracy or better.

Rev1.3 72

Quick Start


Connect the Strain Gauge board to the USBID with a flat flexible cable (FFC). The colored tabs on the

FFC should be facing upwards as shown below in Fig.SG1.

Fig.SG1. Strain Gauge board attached to USBID.

Attach a strain gauge transducer to the screw terminal connector, shown in Fig SG1. A full bridge circuit

is required. All force transducers should be configured this way. For ¼ and ½ bridge circuits, external

matching resistors must be used. Minimum resistance of a strain gauge transducer circuit is 60 Ohms

(measured between excitation and ground or between +v and -v). Excitation for the transducer is with the

two center terminals, labeled EXC and GND. If two transducers are used, excitation for both transducers

should be from these two terminals.

Micro USB

Connector


Gain1 Set Gain2 Set

Ch1

Balance

Ch2

Balance



Rev1.3 73



Start the Fremont USBID software on your PC. The software should appear as shown below in Fig.SG2.

Fig.SG2. Fremont USBID software with Strain Gauge board attached to USBID.

In the Analog Acquisition Parameters box at the top of the window check/uncheck the appropriate

Channels box for which channels you wish to acquire.

Check the Real Time button in the Analog Acquisition box to the right of the plot area and press the Start

button.

Use a small screwdriver to set the balance potentiometers on the Strain Gauge board (Ch1 Balance and/or

Ch2 Balance, shown in Fig. SG1.). Balance should be set to the middle of the full scale range,

approximately 1.65V.

Push on the strain gauge and you should see data something like that shown in Fig.SG3 below.

Rev1.3 74

Fig.SG3. Fremont USBID software during a Real Time acquisition with a strain gauge instrument board

attached to USBID.




All controls will be disabled during the acquisition. Press the STOP button in Analog Acq box to stop the

acquisition.



Rev1.3 75


In the controls described below two similar terms are used but have different meanings.

Sample- A single acquired value.

Point- A point is a value that can represent the information of multiple samples.




these boxes.

Fig.SG4. The USBID is not connected to a USB port. Check the USB cable and connections.

Fig.SG5. The USBID is connected to a USB port but an instrument is not connected to the USBID with a

FFC. Check that the FFC cable is correctly attached between the USBID and an instrument.

Fig.SG6. The USBID is connected to a USB port and an SG sensor board is connected to the USBID.


Analog Acquisition Paramaters Box

Scan Length(pts)- This control is visible for the acquisition types Real Time, Waveform, and Waveform

On Trig set in the Analog Acq box. This control sets the number of points acquired in an acquisition and

the number of points plotted. This is also the number of points saved with Save Current Data button.

Scan Length(vals)- This control is visible for the acquisition types Pk. Detect on Trigger or Statistics set

in the Analog Acq box. For Pk. Detect on Trigger this control sets the number of values scanned for a

peak (or minimum) value. For Statistics this control sets the number of values scanned for a minimum,

maximum, average, and standard deviation.

Pks to Detect- This control is visible when Pk Detect on Trig is checked in the Analog Acq box and sets

the number of maximum (or minimum) points acquired. This is also the number of points saved with Save

Current Data button.

Points- This control is visible when Statistics is checked in the Analog Acq box and sets the number of

points collected. This is also the number of points saved with Save Current Data button. To acquire data

continuously, check the log Data to PC box (only available for Statistics).

Rev1.3 76

Channels Acquired box is used to set if data is acquired for channel1, channel2, or both by checking Ch1

and/or Ch2 box.

Pk Detect Channel sets the channel scanned for a peak or minimum value when Pk Detect on Trig is

checked in the Analog Acq box. If both channels are selected in the Channels Acquired box, the channel

scanned for a peak is set by this box and the value of the other channel is its value at the peak of the

scanned channel.

Acq. Rate Set by Box This box is used to set the rate at which data is acquired and if data is averaged during an acquisition. The

type of Acquisition Rate available is dependent on the acquisition type set in the Acquisition Control box.

Averaging button uses averaging to set the acquisition rate (Fig. SG7). The time between samples can

vary but time data for each sample is saved. This is the best option if filtering is required and a precise

sample rate is not required. This is the only option available for Real Time acquisition. It can also be used

in both Waveform and Waveform on Trig.

Fig.SG7. Acquisition Rate Set by: box with Averaging button checked (Ch1 and Ch2 acquired).

Values Averaged/S control sets the number of values averaged per sample(S). Values are

acquired at ~40,000 values per second for 1 channel and ~20,000 values per second for 2 channels

acquired

Average Rate (S/s) is the approximate sample rate averaged for many samples. The actual rate

between samples will vary but the actual time at acquisition will be saved for each point when data

is saved using Save Current Data. The time value reported for a sample is the current time of the

USBID at the start of averaging for that sample. The USBID time can be set in the Setup tab (see

below).

Clock w/Average- When this button is checked the time between samples is constant and multiple values

are averaged for each sample (Fig.SG8). The number of values to average per sample is set with the

Values Averaged/S control and rate of acquisition of samples is set with the sliding control Acq Rate(S/s).

The maximum value of Acq Rate(S/s) is limited by the number of channels selected and the number of

values averaged . If averaging is desirable and a higher acquisition rate is required but the time between

samples does not have to be constant use the Averaging button.

Rev1.3 77

Fig.SG8. Acquisition Rate Set by: box with Clock w/Average button checked (Ch1 and Ch2

acquired).

Values Averaged/S control sets the number of values averaged per sample(S). Values are

acquired at ~40,000 values per second for 1 channel and ~20,000 values per second for 2 channels

acquired.

Maximum Rate(S/s) is the maximum rate that samples can be acquired and is also the maximum

acquisition rate that can be set with slider. Maximum Rate(S/s) is dependent on Values

Averaged/S and the number of channels acquired. Higher values of Values Averaged/S decrease

Maximum Rate(S/s).

Acq Rate(S/s) is the number of samples acquired per second. The rate can be set from 1S/s to

Maximum Rate(S/s). The value is set with the slider on the track bar. To change the acquisition

rate either click on the pointer of the control and drag or click to the left or right of the pointer

Clock button obtains data at the specified clock rate set with the sliding control (Fig. SG9). No averaging

is used. A single value is acquired per sample. This is the only option available for Statistics in the

Acquisition Control box. This option is also available for Waveform and Waveform on Trig. The time

value for a sample in a saved file is the time of the sample acquisition relative to the start of the

acquisition. The time value of the first acquisition will be zero.

Fig.SG9. Acquisition Rate Set by: box with Clock button checked.

Acq Rate(S/s) is the acquisition rate, number of samples acquired per second. The rate can be set

from 1S/s to 10,000S/s. The value is set with the pointer on the track bar. To change the

acquisition rate either click on the pointer of the control and drag or click to the left or right of the

pointer.

Trigger Box The values in the trigger box are used to set trigger parameters when Waveform On Trigger or Pk. Detect

on Trigger buttons are checked in the Analog Acq box. When one of these buttons is checked and after

pressing the Start Trace button, an acquisition begins when conditions set in the Trigger box are satisfied.

Rev1.3 78

Rising Edge- When button is checked an acquisition is started on the transition from below the

threshold value to above the threshold value. Threshold value is set by the Level(V) control. The

first point after the transition is not saved.

Falling Edge- When button is checked an acquisition is started on the transition from above the

threshold value to below the threshold value. Threshold value is set by the Level(V) control. The

first point after the transition is not saved.

Trig. Source sets the channel or channels to monitor for a trigger. The source is set by checking

Ch1 and/or Ch2 box. A trigger can be initiated by a channel that is not acquired. For example, if

only Ch1 is checked in the Channels Acquired box and Trig. Source is set to Ch2, an acquisition

of channel1 is started when channel2 meets the trigger conditions.

Level(V)- The threshold value that must be crossed to initiate a trigger.



strain gauge instrument this will be SG_0.csv. When a configuration is saved all values that can be


boxes.


Save As... When this button is pressed a dialog pops up and you can save a custom configuration.

If you would like the configuration to be the default configuration when the Fremont software

starts, save the configuration as SG_0.csv.

To recover the unmodified default configuration, close the software, open the folder

c:\Fremont\Config and delete the file SG_0.csv. When the Fremont software is restarted the

default configuration will be recreated in c:\Fremont\Config and the default values loaded.

Note: Do not modify a configuration file in a text editor. Format of the file will be changed and

cannot be read by the Fremont software. Make all changes to a configuration in the Fremont

software and save changes to a configuration file with the Save/Open Config box.

Analog Acq box This box is located to the right of the plot area. The buttons in this box set the type of acquisition.

START- Pressing this button will start an acquisition. Depending on the type of acquisition selected

below the START button, the text on the button will change to either STOP or Acq in Progress. STOP is

shown when the acquisition type selected is Real Time or Statistics (when Log Data checked). To end an

acquisition, press the STOP button. Acq in Progress is shown when the acquisition type selected is

Waveform, Waveform on Trig, Pk. Detect on Trig, or Statistics (when Log Data not checked). Acq in

Progress indicates that the acquisition is being handled by the USBID and the PC program is waiting for

the USBID to indicate the acquisition is complete. When an acquisition has been completed the button

text will change back to START. If you wish to stop an acquisition before the USBID has completed an

acquisition, unplug the USB cable and reattach.

Rev1.3 79

Real Time- When this button is checked data is acquired and displayed in the plot area at a data rate set

by Samples Averaged/pt. Maximum rate is approximately 33 S/s. Data can be saved with Save Current

Data.

Waveform- When this button is checked data will be acquired using parameters set in the Acquisition

Rate Set by: box. Save data acquired with Save Current Data button.

Waveform on Trig button when checked will acquire data when the trigger conditions set in the Trigger

box are met. For example, if the buttons Rising Edge and Ch1 are checked, and the value in Level(V) is

1.75, an acquisition will occur when the voltage of channel 1 increases from a value of less than 1.75V to

a value greater than 1.75V. The condition for a trigger in this case is that the voltage of channel 1 crosses

the level value and is increasing. Save data acquired with Save Current Data button.

Pk. Detect on Trig button when checked will scan the number of values entered in Scan Length(vals) for

a peak when trigger conditions are met. It will then scan for subsequent peaks based on trigger values and

number of peaks to detect entered in Pks to Detect control. Save data acquired with the Save Current Data

button.

Detect Min box when checked will find the minimum rather than the maximum value for Scan

Length(pts).

Statistics button when checked will acquire maximum, minimum, average, and standard deviation for the

number of values entered in Scan Length(vals). The acquisition rate can be set from 1S/s to 2000S/s for a

single channel or 1S/s to 1000S/s for two channels. Two options are available for data logging, set by

checking the Log Data to PC box under the Statistics button:

Log Data to PC box not checked- the maximum number of points collected is set in the Analog

Acquisitions Parameters box with the Points box (maximum points is 166 for 1channel or 83 for

2channel). The time between data sets acquired for statistics will be 695us or 1210us, depending on if one

or two channels acquired. Data is plotted after all points are acquired. Save data acquired with the Save

Current Data button.

The total time for an acquisition is:

t(s) = (no. of channels)*(Scan Length(vals))*Points/(Acq. Rate(S/s))

As an example:

channel1 and channel2 boxes are checked (no. of channels = 2)

Scan Length(vals) = 1000

Points = 50

Acq. Rate(S/s) = 1000

The time for the acquisition is:

t(s) = 2*1000*50/1000 = 100 seconds

If you accidentally start an acquisition that will take two days to complete and this isn’t what you want,

the acquisition can be stopped by unplugging the USB cable and reattaching (any data collected will be

lost).

Rev1.3 80

Log Data to PC box checked- data points are saved to a file and plotted as they are collected. An

acquisition can be stopped at any time by pressing the STOP button. Time between data points is set with

the Measurement Time(s) control.

Measurement Time(s) control sets the time between measurements. This is useful for periodic

sampling of data. For Measurement Time greater than the time required to make an acquisition the

result is periodic sampling of data (first example below). If Measurement Time is less than the

time required to make an acquisition, the total time of an acquisition is the time for acquiring a

single point plus the time for data transfer, ~50ms (second example below).

Examples:

Example1

If Measurement Time(s) = 2




The time required to acquire the point is

t(s) = (no. of channels)*( Scan Length(vals))/ (Acq. Rate(S/s))

= 2*100/1000 = 0.2 seconds

The time between measurements is 2s so every 2 seconds you will acquire data for 0.2

seconds. No data is acquired for 1.8s between the 2s interval.

Example2

If Measurement Time(s) =0.05




The time required to acquire the point is

t(s) = ( Scan Length(vals))/ (Acq. Rate(S/s))

= 2*100/1000 = 0.2 seconds

The time between measurements is 0.05s but this is less than the time required to acquire

the point. The measurement time is then set by the time to acquire the point, t(s). In

addition to t(s) there is ~50ms for data transfer so in this case the time between points will

be ~0.25 seconds. Note that data transfer time is not related to Measurement Time(s). Data

transfer time is dependent on the operating system, for Windows XP data transfer time is

~50ms. For Windows 8 and Windows 10 data transfer time is slightly less. No matter the

operating system, time data in the saved file accurately represents the time at which the

data point was acquired.

Data Location/File: When log data to PC box is checked, all data acquired is automatically saved

to a file on the PC when the START button is pressed. The location and file name of the saved

data is indicated in the text below Data Location/File:.

Rev1.3 81

The file name is the date and time of the start of the measurement (PC system time). For example,

the file name 20160515125604.csv indicates that the acquisition started in 2016(year) in



File format is shown in Fig.SG10. The values saved to the file are acquisition number, time(s),

minimum, maximum, mean, and standard deviation for the channels selected. To the left of the

data columns is a header containing acquisition parameters.

n Time(s) Ch1Min Ch1Max Ch1Mean Ch1StDev AcqType:Statistics AcqRateSetBy:Clock ClockRate:2000 Scan Length:100

0 2025.784 1.642981 1.680358 1.660831 0.008115

1 2026.782 1.639005 1.681949 1.659508 0.008028

2 2027.783 1.641391 1.687515 1.659626 0.00732

3 2028.785 1.637415 1.670815 1.656942 0.007711

4 2029.783 1.6398 1.674791 1.659973 0.007517

5 2030.78 1.6398 1.679563 1.659855 0.007599 Fig.SG10. Saved file format example.

Current Measurement No.- This displays the total number of points that have been measured

and saved to PC memory from the start of the acquisition. This value is only incremented when

the “log Data to PC” box is checked.

Plotted Value- buttons select the type of data plotted in the chart area during an acquisition.

Saved data will contain all four types of values.

Save Current Data- When this button is pressed data shown in the plot area is saved. A Save window

appears and data can be saved to either the default location/file name or a user specified location/file

name. The default location for data saved is to the folder c:\Fremont\Data with a date/time string as the

file name. The date/time file name will be the PC system time when the file is saved. The formatting of

the saved data depends on which type of acquisition has been selected in the Analog Acq box:

Real Time button checked- Saved data is acquisition number(n), time of acquisition(Time(s)), and

voltage from the channels(Chx) selected in the Channels Acquired box. When data has been

overwritten in the plot area, saved data starts from the right of the cursor (oldest data appears first

in the saved file). At the start of an acquisition, when old data is not being overwritten in the plot

area, saved data starts from the right of the plot area.

Waveform button checked- Saved data is acquisition number(n), time of acquisition(Time(s)), and

voltage from the channels(Chx) selected in the Channels Acquired box.

Waveform on Trig checked- Saved data is acquisition number(n), time of acquisition(Time(s)),

and voltage from the channels(Chx) selected in the Channels Acquired box.

Pk. Detect on Trig checked- Saved data is acquisition number(n), time of acquisition(Time(s)),

and the peak voltage from the channel(Chx) selected in the Pk. Detect/Scale Chan box. If both

channels are checked in the Channels Acquired box, the peak voltage of the channel selected in

the Pk. Detect/Scale Chan box is saved as well as the voltage of the other channel at the time of

this peak value. Only one channel is scanned for a peak value.

Statistics checked- The first two columns of saved data are acquisition number(n), and time of

acquisition(Time(s)). The following four to eight columns contain minimum, maximum, mean,

and standard deviation of acquired channel(s) selected in the Channels Acquired box.

Rev1.3 82

To the right of the data columns in all saved data files is a header showing acquisition type and

acquisition values. An example of a saved data file is shown above in Fig. SG10.

The location of the saved file is shown in the text box labeled Data File. On the start of a new

acquisition the text in this box is cleared. This is to indicate to the user that the new data currently

displayed in the plot area has not been saved.

Y Scaling can be used to change the vertical scaling of plotted data. The Maximum value is for a range of

0-3.3V. By changing the values in the Y Max and Y Min control boxes and pressing the Manual button

the vertical scaling is set to the values entered in Y Max and Y Min. Pressing the Maximum button resets

the data range to 0-3.3V. Y Scaling can be reset during acquisition of data or after an acquisition has

completed. You can toggle between the two scales by alternately pressing the Maximum or Manual

buttons.

Setup Tab Controls

The available controls in the setup tab are used to set the clock on the USBID, convert the Time(s)

column in a saved data file to date/time format, use one channel as a scale, and set the voltage band gap

reference value.

The available controls on the setup tab are shown in Fig.SG11.

Fig.SG11. Setup Tab Controls.

Rev1.3 83

Set USBID Time Box The USBID uses a real time clock independent of the PC system clock to measure the time at data




time.















checked.






only.

The figure below (Fig.SG12) shows the result when the button Use System Time is checked, the



USBID.



Rev1.3 84

Fig.SG12. Set USBID time to system time and then read.


Fig.SG13. Control box to convert the time column in a saved file to Date/Time format.

This box is used to convert the time column of saved data from seconds to a date/time format. The

default start time for all acquisitions is seconds from the time the USBID is first powered by being

attached to a USB port. The time can be changed with the Set USBID Time box (see above) to the

System Time, Zero, or a Custom value.

When the Convert Time(s) box is used, three additional date and time columns are added to a new

file containing all of the data from the original file. The three additional columns in the new file

are m/d/yr, hr:min:s, and ms. The ordering of the month, day, and year in the date column can be

specified by checking the appropriate button. The time in the hr:min:s column is in 24 hour

format.

To convert a file:

Choose the converted date format with the three buttons at the top of Convert Time(s) to Date and

Time box. The available options are m/d/yr, yr/m/d, or d/m/yr. The date column in the converted

file will use the selected option of these three as the header.

Press the Open File button. A dialog box titled Open File will appear and you can select the file

for date/time conversion. Select the file for conversion and press the Save button.

The original dialog box will be replaced by one titled Save File with Appended Date/time. Enter a

new file name or use the default file name. The default name is system time at the time of the file

conversion (format of default file name is yyyymmddhhmmss). Press the Save button.

After a file conversion the text in the Convert Time(s) Column to Date and Time box will be

changed, showing the file opened and the new file to which data has been saved. This is shown in

Fig.SG14.

Rev1.3 85

Fig.SG14. Control box after a date/time conversion.

An example of the data columns in a file where time data in seconds has been converted to date

and time and appended to new file containing all of the original data is shown below in Fig.SG15.

n time Ch1

0 5.27E+08 1.667144

1 5.27E+08 1.655705

2 5.27E+08 1.658886

3 5.27E+08 1.660778

n m/d/yr hr:min:s ms time Ch1

0 9/8/2016 22:05:32 132.538 5.27E+08 1.667144

1 9/8/2016 22:05:32 238.525 5.27E+08 1.655705

2 9/8/2016 22:05:32 269.531 5.27E+08 1.658886

3 9/8/2016 22:05:32 301.544 5.27E+08 1.660778 Fig.SG15. Time in seconds converted to date and time format.

Notes:

A file to be converted can not be modified from the original saved data format before conversion.

Any modification of a file from its original format before conversion can result in an error when

the file is converted. The file to be converted can not be open in another application during

conversion or an error will occur.

Rev1.3 86

Scale Box

Fig.SG15a. Scale function allowing an attached force transducer to be used for measuring mass or weight.

This box allows an attached strain gage force transducer to be used as a scale. To use an attached

transducer as a scale, first set the channel the transducer is attached to by checking the appropriate check

box in the Channels Acquired box in the Acquisition tab (only one box should be checked). Also, select

this channel in the Pk. Detect/Scale Chan control. Set the control Sensitivity(unit Mass/V) to 1.000. Press

the START button and then press the Tare button. Place a mass of known value, M, on the transducer and

record the value, V, shown in the box labeled Mass. For the mass, M, calculate the value to be entered in

Sensitivity(unit Mass/V) control using the formula below.

Sensitivity(unit Mass/V) = M/V

Press the STOP button and enter this value in the Sensitivity(unit Mass/V) control. Your force transducer

has now been calibrated as a scale. Press the START button again to use the force transducer as a scale.

To return to the Acquisition tab press the STOP button. Values entered in the Scale box do not modify

values read from the Acquisition tab.

Tare- Pressing this button sets the value shown in the Mass box to zero.

Sensitivity(unit Mass/V)- The value in this control is the scale factor used to convert the voltage read by

the USBID to a mass value, shown in the Mass box.

Values Averaged/reading- The value in this control sets the number of values averaged at ~40kS/s for

each value shown in the Mass box.

VBG value

The value shown in this box is used to calibrate analog measurements, such as strain gauge, current sense,

or differential amplifier measurements. The value is measured from a high precision band gap reference

voltage on the USBID board. Whenever an analog measurement is made, band gap reference voltage is

measured and the calibration value in this box is updated. This value cannot be modified by the user.

Read VBG- This button allows you to read the current value of the calibration value.

Rev1.3 87

Setting Gain

The Strain Gauge/Differential Amplifier instrument board has a nominal gain of 505 with a tolerance of

1%. A method to measure actual gain is given below in Examples.

In many applications a lower gain may be desired. Gain of the Strain Gauge instrument board can be

reduced from the nominal value of 505 to a lower value by attaching external axial resistors to the

chXGain terminals of the Strain Gauge board (shown in Fig.SG1). Each channel can have different gain

values.

Nominal gain is 505 with no external resistor. This gain can be decreased by attaching an external

resistor. The gain, G, with an external resistor, Rg, attached across the terminals of the terminal block

labeled chXGain is

g

g

Rk

RG

++=

100

5005

The resistance Rg in terms of gain (G) is

)505(

)5(100

G

GkRg

−

−=

In the table below, the resistance Rg is calculated for several gain values. The nearest resistor to Rg

available is also shown (nearestR) and gain is calculated with nearestR. Also given is the part number

from Digi-Key for nearestR.

G Rg (kOhm) nearestR(kOhm)G calculated from

nearestRDigi-Key part#

10 1.01 1 9.95 1.0KXBK-ND

20 3.09 3.09 19.99 3.09KXBK-ND

40 7.53 7.5 39.88 7.50KXBK-ND

60 12.36 12.4 60.16 12.4KXBK-ND

100 23.46 23.2 99.16 23.2KXBK-ND

200 63.93 63.4 199.00 63.4KXBK-ND

300 143.90 143 299.24 143KXBK-ND

400 376.19 374 399.51 374KXBK-ND

The table above is just an example of gains that can be obtained with commonly available resistors. Other

gains are possible using a network of resistors in parallel and series. The tolerance of resistors on the

Strain Gage instrument is 1% so gain accuracy of less than 1% is not possible.

Use the highest gain possible that keeps the measured output in the range from 0V to 3.3V for the

expected load on the force transducer.

Balance will change with an external gain resistor. Reset the balance potentiometer on the Strain Gauge

board for the appropriate channel. Balance should be set to the middle of the full scale range,

approximately 1.65V.

Rev1.3 88

Using an External Excitation Voltage

An external excitation can be used but input voltage to any of the ±v1 or ±v2 terminals cannot exceed

3.3V or the instrument could be damaged. Using an external excitation is not recommended. An external

excitation voltage should not exceed the maximum excitation voltage for the strain gauge or force

transducer. The circuit diagram for an external excitation is shown in Fig.SG16.

+v1

-v1

exc

+v2

-v2

gnd

External Ground

External Excitation

Strain Gauge Instrument

Screw Terminal Block

Fig.SG16. Circuit diagram using external excitation.

Rev1.3 89

Examples The first examples show the amplifier used as a strain gauge amplifier. The final examples show how to

use the amplifier as a differential amplifier.

Most of the strain gauge examples use a two axis force transducer where the two axes are perpendicular.

Two full bridge force transducers are mounted on beams at right angles, shown in Fig.SG17. At

resonance, the resonant frequency of CH2 is approximately half that of CH1. This transducer has a

maximum load capacity of a few ounces (<1 N).

Fig.SG17. Image of two axis force transducer used in examples.

The final strain gauge example uses a 500 pound force transducer to measure force required to push out a

pressed insert.

Two differential examples are also given below. The first example measures the resolution of a Digital to

Analog Converter (DAC). The second example measures the gain of the amplifier.

Rev1.3 90

Example1, Real Time Data - A 2.5g mass is added to the channel2 strain gauge circuit and then

removed. This is shown in Fig.SG18.

Fig.SG18. Real Time Data acquisition example showing 2.5gram step.

Rev1.3 91

In saved data, the oldest data (to the right of the vertical red cursor) is saved first. The saved data from the

figure above is shown in Fig.SG19. The acquisition number (n) is numbered from 0 to the value in Scan

Length(pts). The first value of n (n=0) in saved data is the first value to the right of the red cursor. The

last value (n=99 in this example) is the value immediately to the left of the cursor (the most recent data

point). The actual time at data acquisition is also saved and follows the protocol described above.

1.66

1.68

1.7

1.72

1.74

1.76

1.78

1.8

1.82

1.84

0 20 40 60 80 100

Ch

2(V

)

n

Ch2

Ch2

Fig.SG19. Real Time Data acquisition example for 2.5gram step showing saved data for Save Current

Data button press.

Rev1.3 92

Example2, Waveform - Fig.SG20 is an example of a waveform captured when the Waveform button is

checked in the Analog Acq. Box for a 2 axis force transducer. The example uses Clock w/Average. The

time between points plotted(the clock rate) is set by the value set in Acq Rate(S/s) and the number of

values averaged for each point plotted is set in the Samples Averaged/pt box. For this example, 20 points

are collected per second and each of these points is an average of 1000 values. 100 points are acquired so

the time required for the acquisition is 5 seconds (5s = 100pts/20pts/s).

Fig.SG20. Waveform acquisition example using clock with average.

Rev1.3 93

Example3, Waveform on Trig - Fig.SG21 is an example of a waveform captured when the Waveform

on Trig button is checked in the Analog Acq Box for a 2 axis force transducer. The force transducer is

plucked at 450 relative to its axes of sensitivity, resulting in oscillation of the transducer on both axes at

their resonant frequencies. Both channels are captured and acquisition rate is set by Clock. The start of the

acquisition is triggered by the values in the Trigger box, Trigger On: Rising Edge of Ch2 at a Level(V) of

1.675V (the trigger source is set to channel 2 and an acquisition will begin when the voltage on channel 2

increases from a value of less than 1.675V to a value greater than 1.675V).

Fig.SG21. Waveform on Trig acquisition example.

The waveform shows that the force transducer behaves like a damped harmonic oscillator with channel 2

having a resonant frequency of 322.2Hz and channel 1 a resonant frequency of 649Hz.

The next two examples use the same excitation used to produce the waveform shown in Fig.SG21.

Rev1.3 94

Example4, Pk Detect on Trig1- Peak Detect on Trig is used to find maximum values (or minimum). In

Fig.SG22, the transducer is made to oscillate as in the previous example but now the waveform is scanned

for peaks on channel 2. The number of points scanned for a peak is 10 and the number of Pks to Detect is

100. Both channels are captured, Pk. Detect/Scale Chan is set to channel 2, and acquisition rate is set by

Clock. The start of a peak detect is triggered by the values in the Trigger box, Trigger On: Rising Edge of

Ch2 at a Level(V) of 1.675V (the trigger source is set to channel 2 and a peak detect will begin when the

voltage on channel 2 increases from a value of less than 1.675V to a value greater than 1.675V). Once the

start button is pressed in Pk Detect data acquisition is controlled by the USBID and will continue until all

peaks are detected. The only way to stop an Acq in Progress is by unplugging the USB cable (resetting

the USBID).

Fig.SG22. Pk Detect on Trig acquisition example for channel 1.

Since the peak detect channel is set to 2, 10 values of channel 2 are scanned for a maximum value after

the trigger conditions are satisfied. This value is reported as the peak for channel 2. The value shown for

channel 1 is the value of channel 1 at the peak value of channel 2. The peak detect channel (channel 2) has

a resonant frequency of approximately half that of channel 1. At the beginning of the measurement when

channel 2 is at a peak channel 1 will also be at approximately a maximum (see Fig.SG21). The resonant

frequencies of the 2 channels do not differ exactly by a factor of 2 so the maximum value of Ch1 will drift

away from the maximum value of Ch2 and you get the result shown above.

Rev1.3 95

Example5, Pk Detect on Trig2- In Fig.SG23, the transducer is made to oscillate as in the previous

example but now the waveform is scanned for peaks on channel 1. The number of points scanned for a

peak is 6 and the number of Pks to Detect is 100. Both channels are captured, Pk. Detect/Scale Chan is set

to channel 1, and acquisition rate is set by Clock. The start of a peak detect is triggered by the values in

the Trigger box, Trigger On: Rising Edge of Ch1 at a Level(V) of 1.675V (the trigger source is set to

channel 1 and a peak detect will begin when the voltage on channel 1 increases from a value of less than

1.675V to a value greater than 1.675V). Once the start button is pressed in Pk Detect data acquisition is

controlled by the USBID and will continue until all peaks are detected. If the text on the button is Acq in

Progress, the only way to stop the acquisition is by unplugging the USB cable (resetting the USBID). This

will in no way harm the USBID or the attached instrument.

Fig.SG23. Pk Detect on Trig acquisition example for channel 1.

The peak detect channel (channel 1) has a resonant frequency of approximately twice that of channel 2 so

when channel 1 is at a peak channel 2 will be either at a maximum or minimum (see Fig.SG21). Since

Ch1 frequency is slightly higher then twice that of Ch2 the data shows beats as shown above in Fig.

SG23.

Rev1.3 96

Example6, Statistics1- Statistics collects the maximum, minimum, average, and standard deviation for a

number of values (Scan Length(vals)). Fig.SG24 shows an example of statistics collected for channel 2 of

the waveform shown in Fig.SG21. At a data rate of 2000val/s, 30 values are collected and statistics are

calculated for the 30 values to produce one Point set. This is repeated 50 times to produce the plot shown

in Fig.SG24 where maximum value has been plotted.

Fig.SG24. Statistics acquisition example1 for channel 2.

Each data point shown in Fig.SG24 is for 15ms of the waveform shown in Fig.SG21. This waveform has

a wavelength of ~3ms so a data point in Fig.SG24 is the maximum value for 5 wavelengths.

Rev1.3 97

In Fig.SG25, the full data file of the above acquisition is plotted, showing minimum, maximum, average,

and standard deviation. The minimum and maximum values show the envelope of the harmonic

oscillation and, with the time data, a decay rate can be calculated.

Force Transducer Harmonic Oscillation Decay Time

0

0.5

1

1.5

2

2.5

3

3.5

0 100 200 300 400 500 600 700 800

Time(ms)

Vo

lta

ge

(V)

Ch2Min

Ch2Max

Ch2Mean

Ch2StDev

Fig.SG25. Statistics acquisition example for channel 2. Plot of saved data file.

Rev1.3 98

Example7, Statistics2- In this example data is logged to a file on the PC. Logging data to the PC is useful

when you want to periodically sample data and acquire many data points over a long period of time.

There is no limit to file length. This example is similar to the above example. The primary difference is

that for each data point saved there is a 30-60ms dead space for data transfer across the USB and during

this time no data is acquired. Although data transfer rates may vary based on operating system, time data

in the saved file is correct. Time data is acquired by the USBID at time of acquisition and is independent

of transfer time. Fig.SG26 shows a data acquisition using the same parameters used in Statistics example1

with the log Data to PC box checked.

Fig.SG26. Statistics acquisition example2 for channel 2 with log data to PC button checked.

In Fig.SG26 the time between points is approximately 3 times that of the points in Figs.SG24 and SG25

but it is an accurate description of the same waveform. This is shown in Fig.SG27, a plot of the saved data

file with data from Statistics example1 superimposed on data from Statistics example2.

Rev1.3 99

Force Transducer Harmonic Oscillation Decay Time

0

0.5

1

1.5

2

2.5

3

3.5

0 100 200 300 400 500 600 700 800

Time(ms)

Vo

lta

ge

(V)

Ch2Min

Ch2Max

CH2Min Log Data to PC

CH2Max Log Data to PC

Fig.SG27. Statistics acquisition example for channel 2. Plot of saved data files compared.

Rev1.3 100

Example8, Push out force of a pressed insert. In this example the force required to push out a pressed

insert is measured. The inserts are standoffs with a 4-40 internal thread. The inserts have been pressed

into clearance holes recommended by the insert manufacturer. The material the inserts have been pressed

into is 6061 extruded aluminum. The inserts are pushed out using an arbor press and push out force is

measured using a 500 pound range force transducer. Push out force is here defined as the maximum force

required to press out the insert. Prior to force on the insert reaching this maximum value, displacement of

the insert may have occurred due to plastic deformation of the aluminum. Fig.SG28 shows the test setup.

Fig.SG28. Push out force measurement hardware.

Arbor Press

Test sample with

pressed inserts

Force Transducer

Rev1.3 101

Push out force for 11 inserts was measured. The samples were measured using a Real Time measurement.

Test parameters are shown below in Fig. SG29, a screen capture of a typical push out force measurement

for an insert.

Fig.SG29. Push out force measurement showing software settings and saved data.

Rev1.3 102

Figure SG30 below shows the data from the measurement shown above scaled from volts to pounds of

force.

Push Out Force Example

0

50

100

150

200

250

0 50 100 150 200 250 300

Point Number

Forc

e (

pounds)

Fig.SG30. Push out force measurement showing saved data from Fig. SG29 rescaled from volts to

pounds.

The table below summarizes the push out force for the 11 pressed inserts.

maximum(lb) 230

minimum(lb) 191

mean(lb) 211

stdev(lb) 11.9

Rev1.3 103

For some of the measurements high speed measurements of push out force were made which show start of

plastic deformation (yield strength), work hardening (yield strength to shear failure) and ultimate strength

of the insert in aluminum. This is shown below in Fig.SG30a.

Fig.SG30a. High speed push out force measurement showing yield strength, ultimate strength, and shear

failure for a pressed insert.

Push Out Force for 4-40 Standoff in 1/8" 6061 Al

100

120

140

160

180

200

220

240

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Time(s)

Fo

rce

(lb

) Yield Strength, Plastic Deformation

Begins

Shear Failure Begins

Rev1.3 104

Differential Amplifier Examples

Two differential examples are given below. The first example measures the resolution of a Digital to

Analog Converter (DAC). The second example measures the gain of the amplifier.

Example9, Differential Amplifier1 – In this example the strain gauge instrument is used as a differential

amplifier and measures the voltage resolution of a digital to analog converter (DAC) used in a voice coil

driver. The figure below (Fig.SG31) shows the wiring diagram of the Strain Gauge Instrument board to

the DAC circuit.

Fig.SG31. Wiring diagram showing the strain gauge instrument used as a differential amplifier.

The DAC in this example is a voice coil driver, courtesy of Nanometronix, used in a nanoindenter. The 10

ohm resistor in Fig.SG31 is used in place of the voice coil in the nanoindenter.

The DAC can be driven with full step or 1/10 step resolution. In full step the DAC resolution is ~100uV

per step. In 1/10 step, resolution is ~10uV. Fig.SG32 shows full step resolution and Fig.SG33 shows 1/10

step resolution.

+v1

-v1

exc

+v2

-v2

gnd

Strain Gauge

Instrument

Screw Terminal

Block


Board

10 Ohm

External Digital to Analog Converter

Circuit

Digital to Analog

Converter

V+ Out

V- Out

DAC gnd

I2C Data

Clock

+5V

Rev1.3 105

Digital to Analog Converter Showing Full Step Resolution

0

50

100

150

200

250

300

350

400

450

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Measurement Number

mic

roV

olt

s

Fig.SG32. Full step resolution of a digital to analog converter.

Rev1.3 106

Digital to Analog Converter Showing 1/10 Step Resolution

0

5

10

15

20

25

30

35

40

45

50

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Measurement Number

mic

roV

olt

s

Fig.SG33. 1/10 step resolution of a digital to analog converter.

In Figs.SG32 and SG33 data is measured using averaging. 10 values are averaged per point. 1000 points

are acquired for each DAC value (2 acquisitions of 500 pts are made for each DAC value, plotted data

shows 10 acquisitions). Data is then concatenated and plotted using a moving average of 100 points.

Rev1.3 107

Example10, Differential Amplifier2 – In this example the strain gauge instrument is used as a

differential amplifier and, with an added external resistor network, measures the gain of the strain gauge

instrument.

The added circuit is shown below in Fig.SG34.

Fig.SG34. Wiring diagram showing the strain gauge instrument used as a differential amplifier with

circuitry to measure gain.

When the switch is open, the voltage drop across the 33 Ohm resistor on the left will be zero because no

current is flowing through the resistor. When the switch is closed the voltage between +v1 and –v1 (V)

will be the voltage difference across the 33 Ohm resistors in parallel.

By Ohms law, the differential voltage, V, when the switch is closed will be

+

=

3340

33*)3.3(

k

VV

The differential voltage measured by the strain gauge instrument, VswitchClosed, between +v1 and –v1 will

be increased by a gain factor, G. Also, the offset voltage needs to be considered. When the switch is open

the offset voltage, Voffset, can be measured. It should be set to ~1.65V with Ch1 Balance potentiometer,

shown in Fig. SG1. A measurement made while the switch is open will be Voffset.

With the gain factor and voltage offset accounted for, the voltage when the switch is closed is

VswitchClosed = Voffset + GV

Substituting in V to the above expression and solving for G gives

+−=

33*)3.3(

)3340(*)(

V

kVVG

offsetedswitchClos

Switch

3.3V

+v1

-v1

exc

+v2

-v2

gnd


Screw Terminal Block 10KΩ

10KΩ

33Ω 33Ω

Rev1.3 108

An example of acquired data is shown below in Fig.SG35. Data is first acquired with the switch open to

measure Voffset. The switch is then closed to measure VswitchClosed.

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

3.5

0 100 200 300 400 500 600

Point Number

Vo

ltag

e (

V)

Ch1

Voffset

VswitchClosed

Fig.SG35. Data acquired during a Real Time acquisition showing the measured change in voltage when

the switch illustrated in Fig.SG31 is closed.

In the data shown above, VswitchClosed - Voffset = 1.371V.

Plugging this into the equation for gain, G, gives

G = 1.371V*40033Ω/108.9VΩ = 504

This result falls within the expected range of the actual value. The nominal gain of the Strain Gauge is

G = 505±5.

The tolerance in the value is based on the tolerance of the resistors used to set the nominal gain (505) and

the tolerance of the resistors in the resistor network used to measure this gain, both are ±1%.

Rev1.3 109

Force Transducer and Strain Gauge Basics

A force transducer with a full bridge circuit is built from 4 strain gauges that act like resistors. Two of the

strain gauges will be stretched and 2 will be compressed. Four strain gauges are used to compensate for

thermal fluctuations and also provide a gain of 2. Most force transducers use a full bridge circuit.

When a strain gauge is stretched, resistance increases because the electricity must flow a greater distance

and the area through which the electricity flows has been reduced. When a strain gauge is compressed,

resistance decreases because the electricity flows through a shorter distance and the area through which

the electricity flows has been increased.

Think of it like water flowing through a pipe: a long pipe with small diameter will have low flow (high

resistance) and a short pipe with large diameter will have high flow (low resistance).

The Strain Gauge instrument measures the difference in resistance between the strain gauges compressed

and the strain gauges stretched when used with a full bridge force transducer.

The figure below shows a typical strain gauge. Current flows a long distance through small traces. When

the strain gauge is stretched, the resistance of the strain gauge increases because length of conductor

through which the current flows increases. When voltage (resistance) is measured across the strain gauge,

small differences in the dimensions of the strain gauge are accentuated because of the long trace length,

(cross sectional area is also significant). When the strain gauge is compressed resistance decreases.

Typical dimensions of a strain gauge are a few millimeters per side.

When no force is applied, the simplest full bridge force transducer can be modeled as 4 resistors of equal

value in a bridge circuit, shown below.

R R

R R

1

2

3

4

Rev1.3 110

The terminals on opposite sides of the bridge are either excitation or signal terminals. For example, in the

figure above, terminals 1 and 3 could be used for excitation and 2 and 4 could be used for signal. Because

of the symmetry of the circuit, 1-3 could be signal and 2-4 could be excitation terminals.

Also because of the symmetry of the circuit, if 2 and 4 are used for excitation, it does not matter which is

positive and which is ground. Similarly, 1 and 3 can be transposed for the signal. What will change when

terminals are transposed is the polarity of the signal. For example, set terminal 1 as exc and 3 as gnd,

terminal 2 as +v1 and 4 as –v1, and balance the bridge to 1.65V when no force is applied to the force

transducer. Now apply a force to the transducer that gives an output of 1.95V (1.65V+0.3V). Now if

terminal 1 and 3 are transposed (terminal 1 = gnd, terminal 3 = exc), when the same force is applied to

transducer in the same direction the output will be 1.35V (1.65V-0.3V).

How to find +Signal, -Signal, +Excitation, -Excitation (+S, -S, +E, -E)

Sometimes the output leads of force transducers are not labeled. To determine the leads you will need a

multimeter to measure the resistance between leads. For simple force transducers with no temperature

compensation resistors, what you will be looking for are the sets of leads with the highest resistance.

From the diagram above, the resistance between terminals 1 and 3 will be R. The resistance between

terminals 2 and 4 will also be R. These 2 sets of leads will be signal and excitation (1-3 = signal, 2-4 =

excitation). The resistance of 1-2 and 1-4 will be ¾R.

Leads are usually color coded. Red and black leads frequently indicate excitation (exc, gnd). The other 2

leads are signal (+v1, -v1). Some force transducers use black and white leads for excitation, so check

resistances between leads with a multimeter to verify excitation and signal leads(see example below).

Some force transducers contain temperature compensation resistors. The compensation resistors will be

on the excitation terminals. This results in a useful rule: the 2 leads with the highest measured resistance

should be used for excitation, the remaining 2 leads are signal leads(V+,V-). The resistance between the

remaining two leads should have a resistance near a commonly available strain gauge (120, 350,

1000ohm). An example is given below. The lead colors are white(W), black(B), red(R), and green(G).

The table shows the measured resistance between all the leads and the figure at the left is the equivalent

circuit, showing strain gauges with resistance of 350 Ohm and temperature compensation resistors with

resistance of ~97 Ohm.

Wires Resistance(Ohms)

G->W 350 Signal Leads

G->R 359.5

G->B 360

W->B 360

W->R 359.6

R->B 546.8 Excitation Leads

On the Strain Gauge Instrument board, excitation terminals are labeled exc and gnd. There are 2 sets of

signal terminals labeled +v1, -v1, and +v2, -v2. When two force transducers are used, both transducers

use the same excitation, exc and gnd.

R B

G

W

350 350

350 350

97.5 97

Rev1.3 111

Specifications Absolute maximum ratings for Strain Gauge Instrument I/O

+v1,-v1,+v2,-v2 Voltage(1): -0.5V to 3.8V

+v1,-v1,+v2,-v2 Current(1): 10mA

Excitation Current: 100mA

Operating Temperature: -350C to 850C

Exceeding these values may cause permanent damage to the device. Operating the device at maximum

values for long periods of time may cause degradation of the device.

(1) Inputs are diode clamped to the supply voltage rails (0V and 3.3V). If the input voltage exceeds the

supply voltage values current must be limited to 10mA to prevent device damage.

Flat Flexible Cable


Width: 3.5mm (0.138”)

Length: 300mm (11.8”) as supplied with SG Instrument board




SG Instrument Board and USBID Board Physical Specifications (nominal)


Strain Gauge Instrument board

Mass: 6.77g


1.25 (31.75)

0.125 (3.17)

1.00 (25.4) 0.125 (3.17)

1.25 (31.75)

Rev1.3 112

USBID

Mass: 2.35g


0.75 (12.7)

1.00 (25.4)

0.125 (3.17)

.080 (20.32)

0.125

(3.17) (10.

16)

Rev1.3 113

6. Current Sense

The current sense instrument is used to measure the current through circuits. An external voltage source

of 4.5V to 15V is required. A voltage regulator on the instrument board converts the externally applied

voltage to 3.3V.

• Instrument gains of 25 and 100 available. The 25 gain instrument board can be used for current

measurement up to 1000 mA and the 100 gain instrument board is recommended for current

measurements of less then 200 mA.

• Acquisition rates from 1S/s to 10,000S/s.

• mAh measurement for battery life estimation.

• 12 bit resolution.

• Low pass filtering in software by averaging data.


o Real Time- Continuous acquisition of data at ~30S/s.

o Waveform- One shot data acquisition of up to 500 points at up to 10kPts/s.

o Waveform On Trigger- One shot data acquisition of up to 500 points when trigger

conditions are met at up to 10kPts/s.

o Statistics - Continuous acquisition of maximum, minimum, average, and standard

deviation. Scan length for statistics and acquisition rate are set in software.

▪ Acquired statistics can be automatically saved to a PC file for unlimited data

acquisition length.

• Trigger can be used to initiate an acquisition.

o Trigger level and trigger on rising or falling edge set in software.

• High accuracy voltage reference on USBID provides 0.04% accuracy or better.

• Voltage output to the device being measured is reported in saved data files.

Rev1.3 114

Quick Start

For this quick start example a 1Ω resistor is used as the sense resistor, Rsense. A 499Ω resistor, Rload, is

used as the load across the voltage output (Vout to gnd).


Connect the Current Sense board to the USBID with a flat flexible cable (FFC). The colored tabs on the

FFC should be facing upwards as shown below in Fig. CS1.

Rload and Rsense are not shown in Fig. CS1.

With power supply off, attach power supply leads to Vin screw terminals. Polarity must be correct or the

current sense board and the USBID could be damaged. Polarity is indicated on the current sense board

and shown in Fig. CS1. Power supply voltage must be between 4.0V and 15V. The power supply voltage

is converted to 3.3V by a voltage regulator on the current sense board.

Rev1.3 115

Fig. CS1 Current Sense Board attached to USBID.

Attach a sense resistor across Rsens. The sense resistor used in this example is a 1.00Ω resistor.

Attach a load resistor or device across Vout, between Vout and gnd. The load used in this example is a

499Ω resistor.

Attach a USB cable to the USB connector on the USBID and to a USB port on your PC. An LED should

now start flashing on the USBID indicating connection to a USB port.

Attach the external power supply (4V-15V) to the Vin and GND terminals. Vin is the positive connection

and GND is the negative.


+5V Voltage Supply

1Ohm Sense Resistor

499Ohm

Load

Resistor



Rev1.3 116

Turn on the power supply. Voltage should not be applied across Vin when the USBID is not connected to

a USB port.

Start the Fremont USBID software on your PC. The software should appear as shown below in Fig.CS2.

Fig. CS2 Fremont USBID software with Current Sense board attached to USBID.

In the upper tool strip are two text boxes indicating USBID status and the type of device attached. If a

current sense instrument is attached these two boxes will appear as shown in Fig. CS2.

Enter the sense resistor value in the Sense Resistor(Ohms) control. For all measurements make sure that

this value is correct. The USBID does not measure this value.

In the Acquisition Control box to the right of the plot area check the Real Time radio button.

Press the START button in the Acquisition Control box.

Values will now begin to be plotted in the chart area. This is shown in Fig. CS3 below.

Rev1.3 117

Fig. CS3 Data acquisition example.




All controls will be disabled during the acquisition. Press the STOP button in Analog Acq box to stop the

acquisition.



Rev1.3 118


Status Boxes



these boxes.

Fig.CS4. The USBID is not connected to a USB port. Check the USB cable and connections.

Fig. CS5. The USBID is connected to a USB port but an instrument is not connected to the USBID with

an FFC. Check the FFC cable is correctly attached between the USBID and an instrument.

Fig. CS6. The USBID is connected to a USB port and a Current sensor board is connected to the USBID.


and numeric entry fields. Text in bold face type indicates the label that is shown on these.


Analog Acquisition Parameters

The box at the top of the screen labeled Analog Acquisition Parameters is used to set values used for an

acquisition and data plotted.

no. of Pts. is the number of values that will be plotted in the plot area. It is also the number of values

acquired for a Real Time, Waveform, and Waveform on Trig acquisition.

Sense Resistor (Ohms) Enter the value of the sense resistor attached across Rsense on the current sense

board here.

Voffset(mV) is a calibration constant that corrects a voltage offset in the current sense amplifier. This

value is dependent both on the sense resistor and the current sense instrument. It will have a unique value

for each combination of sense resistor and current sense board. See current sense calibration below to

measure this value for your instrument.

Rev1.3 119

G multiplier is a calibration constant that is a correction of the nominal gain of the current sense

amplifier. This value is dependent on the current sense instrument. It will have a unique value for each

current sense board. See current sense calibration below to measure this value for your instrument.

Acq. Rate Set by This box is used to set the rate at which data is acquired and if data is averaged during an acquisition. The

type of Acquisition Rate available is dependent on the acquisition type set in the Acquisition Control box.

Averaging button uses averaging to set the acquisition rate (Fig. CS7). The time between samples can

vary but time data for each sample is saved. This is the best option if filtering is required and a precise

sample rate is not required. This is the only option available for Real Time acquisition. It can also be used

in both Waveform and Waveform on Trig.

Fig. CS7 Acq. Rate Set by Averaging.

Values Averaged/S is the number of values averaged per sample(S). Values are acquired at

~20,000 values per second.

Average Rate (S/s) is the approximate sample rate averaged for many samples. The actual rate

between samples will vary but the actual time at acquisition will be saved for each point when data

is saved using Save Current Data. The time value reported for a sample is the current time of the

USBID at the start of averaging for that sample. The USBID time can be set in the Setup tab (see

below).

Clock w/Average- When this button is checked the time between samples is constant and multiple values

are averaged for each sample (Fig. CS8). The number of values to average per sample is set with the

Values Averaged/S control and rate of acquisition of samples is set with the sliding control Acq Rate(S/s).

The maximum value of Acq Rate(S/s) is limited by the number of values averaged . If averaging is

desirable and a higher acquisition rate is required but the time between samples does not have to be

constant use the Averaging button.

Fig. CS8 Acq. Rate Set by Clock w/Average

Values Averaged/S is the number of values averaged per sample.

Rev1.3 120

Maximum Rate(S/s) is the maximum rate that samples can be acquired and is also the maximum

acquisition rate that can be set with slider. Maximum Rate(S/s) is dependent on Values

Averaged/S. Higher values of Values Averaged/S decrease Maximum Rate(S/s).

Acq Rate(S/s) is the number of samples acquired per second. The rate can be set from 1S/s to

Maximum Rate(S/s). The value is set with the slider on the track bar. To change the acquisition

rate either click on the pointer of the control and drag or click to the left or right of the pointer.

Clock button obtains data at the specified clock rate set with the sliding control (Fig. CS9). No averaging

is used. This is the only option available for Measure mAh in the Acquisition Control box. This option is

also available for Waveform and Waveform on Trig. The time value for a sample in a saved file is the

time of the sample acquisition relative to the start of the acquisition. The time value of the first acquisition

will be zero.

Fig. CS9 Acq. Rate Set by Clock.

Acq Rate(S/s) is the acquisition rate, number of samples acquired per second. The rate can be set

from 1S/s to 10,000S/s. The value is set with the pointer on the track bar. To change the

acquisition rate either click on the pointer of the control and drag or click to the left or right of the

pointer.

Trigger box is used to set trigger parameters when Waveform On Trig is selected in the Acquisition

Control box.

Level(mA) sets the level in milliamps when an acquisition will begin.

Rising Edge button when checked will force an acquisition when current rises from below

Level(mA) to a value above Level(mA).

Falling Edge button when checked will force an acquisition when current falls from a value above

Level(mA) to a value below Level(mA).

The accuracy of the trigger level depends on proper calibration of your current sense instrument (see

Current Sense Calibration below). This box is only enabled when Waveform On Trig button is checked in

Acquisition Control box. Trigger examples can be seen in the chapter Strain Gauge/Differential

Amplifier.

Rev1.3 121



current sense instrument this will be Current_0.csv. When a configuration is saved all values that can be


boxes.


Save As... When this button is pressed a dialog pops up and you can save a custom configuration.

If you would like the configuration to be the default configuration when the Fremont software

starts, save the configuration as Current_0.csv.


and delete the file TC_0.csv. When the Fremont software is restarted the default configuration will be


Note:




Acquisition Control Box This box is located to the right of the plot area. The buttons in this box set the type of acquisition.

Real Time

This button will acquire data and display it in the plot area at a data rate set by Samples Averaged/pt.

Maximum rate is approximately 30 S/s. The box labeled Vout(V) shows the voltage output to the device.

Vout(V) indicator shows the voltage output to the device attached across the Vout and gnd

terminals of the current sense instrument board. Vout should be monitored to make sure the

voltage requirement of the device attached to Vout is met. The value measured at Vout is based on

the voltage regulator on the USBID board (nominal value 3.3V with 2% tolerance). This value can

differ from the actual voltage across Vout because the voltage regulator on the current sense board

also has a 2% tolerance. This means that the actual voltage across Vout might be 3.3V but could

be measured as3.27V if the voltage regulator on the USBID is only supplying 3.27V. The USBID

can not measure a voltage greater than the voltage of its own regulator.

To stop the acquisition press the STOP button. Data can be saved with the Save Current Data button.

Values saved are point number, time at acquisition, Vout, and current in mA. Time at acquisition is the

current clock time of the USBID. This value can be set to zero or the system time of your PC (see below

in the description of Setup tab controls). Data is saved as oldest value first. The value immediately to the

right of the vertical cursor is n=0 and the value at the cursor is n=Plot Length(S)-1.

Waveform

Rev1.3 122

This button will acquire a single waveform when the START button is pressed. The number of points

acquired and data rate are set in the Acq Rate Set by: box.

Save data acquired with Save Current Data button. Values saved are point number, time at acquisition,

Vout, and current in mA. The zero value of time at acquisition is when the acquisition begins. In a saved

file, at the right of the column header, acquisition parameters are shown.

Waveform On Trig

This button will acquire data when the trigger conditions set in the Trigger box are met. For example, if

the button Rising Edge is checked and the value in Level(mA) is 0.1, an acquisition will occur when the

current increases from a value of less than 0.1mA to a value greater than 0.1mA. The condition for a

trigger in this case is that the current crosses the level value and is increasing. See the chapter “Strain

Gauge/ Differential Amplifier” for plotted data of trigger acquisitions.

Save data acquired with Save Current Data button. Values saved are point number, time at acquisition,

Vout, and current in mA. The zero value of time at acquisition is when the trigger condition is first met. In

a saved file, at the right of the column header, acquisition parameters are shown.

Statistics

An acquisition with this button selected will collect statistics such as minimum, maximum, average, and

standard deviation of current. The charge used by an attached device is also reported as mAh. This option

can be used to determine the power usage of a device and expected battery life when the device uses a

battery.

Data is acquired for a time window set in the Update Rate(s) control. Data will be acquired for the period

of time set in this control at the acquisition rate set in the Acq. Rate Set by: control box. For example, if

Acq. Rate(S/s) is 500 and Update Rate(s) is 3 seconds, 500 samples per second will be acquired for 3

seconds, resulting in 1500 total values for each data point. The mean, maximum, minimum, standard

deviation, start value, and end value of these values are then saved (dependent on the amount of data

acquired, set with MinVals or MaxVals). The value mAh is a sum of all data points from the start of the

measurement, beginning when the Start button is pressed in the Acquisition Control box. To stop a

measurement, press the STOP Trace button.

The indicators and controls for the Measure mAh option are described below.

Two options are available for the amount of data acquired, MinVals or MaxVals.

MinVals

When this button checked will acquire the following data at a maximum rate of 3000S/s. The text

following the comma is the column header in a saved data file.

acquisition number, n

time at start of measurement, Tstart(s)

time at finish of measurement, Tfinish(s)

output voltage at start of measurement, VoutStart(V)

output voltage at finish of measurement, VoutFinish(V)

average current during measurement period, IAve(mA)

Rev1.3 123

mAh used by device across Vout from start of measurement, mAh from Start

At the right of the column header acquisition parameters are shown.

See Real Time measurement above for a description of Vout measurements.

Time values saved use the current clock time of the USBID. This value can be set to zero or the

system time of your PC (see below in the description of Setup tab controls).

MaxVals

When this button checked will acquire all of the values acquired in MinVals but also includes

statistics on current and Vout during the measurement. The increased processor load results in a

slower maximum sampling rate of 1000S/s. The following data is acquired. The text following the

comma is the column header in a saved data file.

acquisition number, n

time at start of measurement, Tstart(s)

time at finish of measurement, Tfinish(s)

current at start of measurement, Istart(mA)

current at finish of measurement, Ifinish(mA)

average current during measurement period, IAve(mA)

maximum current during measurement period, IMax(mA)

minimum current during measurement period, IMin(mA)

standard deviation of the current during measurement, IstDev(mA)

average voltage output during measurement period, VoutMean(V)

maximum output voltage during measurement period, VoutMax(V)

minimum output voltage during measurement period, VoutMin(V)

standard deviation of voltage during measurement period, VoutStDev(V)

energy consumed during measurement period (Joules), Energy(W*s(J))

mAh used by device across Vout from start of the measurement, mAh from Start

At the right of the column header acquisition parameters are shown.

See Real Time measurement above for a description of Vout measurements.

Time values saved use the current clock time of the USBID. This value can be set to zero or the

system time of your PC (see below in the description of Setup tab controls).

Update Rate (s) Data will be acquired for the period of time set in this control at the acquisition

rate set in the Acq. Rate Set by: control box. For example, if Acq. Rate(S/s) is 500 and Update

Rate(s) is 3 seconds, 500 samples per second will be acquired for 3 seconds, resulting in 1500 total

values for each data point. The maximum value of this control is 360,000s (100h). If you set this

control too high and you want to stop the measurement, unplug the USB cable from the USBID,

close the Fremont program and then restart the Fremont program.

log Data (File...\Data\) check box when checked will save data to a file on the hard drive for each

point collected at the rate set by Update Rate(s) with a csv file format (comma separated value).

The file name uses a date/time string for the file name and this file name is written below the log

Rev1.3 124

Data checkbox. For example, if the file name below the check box is 20160504122831.csv, this

indicates the file will be saved in the C: drive in the folder Fremont\Data. The file string format is

year/month/day/time, which for this example indicates 2016 May 4 12 AM 28minutes 31seconds.

When data is saved to the hard drive with this option, there will be a delay of 20-50ms between

finish time of a measurement and the start time of the next measurement. This is due to the time

required for transfer of data across the USB interface. The mAh calculation uses the start and

finish time of the measurement (Tstart(s) and Tfinish(s)) to calculate mAh, giving an accurate

value of mAh.

Average Current (mA) is the average current for the most recent measurement point. It is the

average current for a number of samples which is the product of Update Rate (s) and Acq.

Rate(S/s). For example, if Update Rate (s) is 5 and Acq. Rate(S/s) is 100, this will be the average

current of 500 points collected during 5 seconds.

mAh from Start is a measure of the total charge that has flowed through the output terminals

since the Start button was pressed. The unit mAh is used to allow easy calculation of expected

battery life, usually measured in mAh. An example of battery life calculation is given below in

examples.

Save Current Data When this button is pressed, data shown in the plot is saved. A Save window appears

and data can be saved to either the default location/file name or a user specified location/file name. The

values saved depend on the type of acquisition (see above). The location of the saved file is shown in the

text box labeled Data File. Do not change any value in the numeric entry boxes, check boxes, or radio

buttons before saving data. If any value is changed before data is saved, data will be corrupted. On the

start of a new acquisition the text in this box is cleared. This is to indicate to the user that the new data

currently displayed in the plot area has not been saved.

Rev1.3 125

Setup Tab Controls

The available controls in the setup tab are used to set the clock on the USBID, convert the Time(s)

column in a saved data file to date/time format, and set the band gap reference voltage value.

The available controls on the setup tab are shown in Fig.CS10.

Fig.CS10. Setup Tab Controls.

Set USBID Time Box The USBID uses a real time clock independent of the PC system clock to measure the time at data




time.

The time set in this box appears in saved data files for Real Time and Measure mAh acquisitions.

Waveform and Waveform on Trig acquisitions always measure time from the start of the acquisition.















checked.



Rev1.3 126




only.

The figure below (Fig.CS11) shows the result when the button Use System Time is checked, the



USBID.



Fig.CS11. Set USBID time to system time and then read.

Convert Time(s) Column to Date and Time Box This box is used to convert the time column of saved data from seconds to a date/time format. The default



or a Custom value.

Fig.CS12. Control box to convert the time column in a saved file to Date/Time format.





To convert a file:

Choose the converted date format with the three buttons at the top of Convert Time(s) to Date and

Time box. The available options are m/d/yr, yr/m/d, or d/m/yr. The date column in the converted

file will use the selected option of these three as the header.

Press the Open File button. A dialog box titled Open File will appear and you can select the file

for date/time conversion. Select the file for conversion and press the Save button.

Rev1.3 127

The original dialog box will be replaced by one titled Save File with Appended Date/time. Enter a

new file name or use the default file name. The default name is system time at the time of the file

conversion (format of default file name is yyyymmddhhmmss). Press the Save button.

After a file conversion the text in the Convert Time(s) Column to Date and Time box will be

changed, showing the file opened and the new file to which data has been saved. This is shown in

Fig.CS13.

Fig.CS13. Control box after a date/time conversion.

An example of the data columns in a file where time data in seconds has been converted to date

and time and appended to new file containing all of the original data is shown below in Fig.CS14.

The data shown is for a Real Time acquisition.

Fig.CS14. Time in seconds converted to date and time format.

Notes:

A file to be converted can not be modified from the original saved data format before conversion.

Any modification of a file from its original format before conversion can result in an error when

the file is converted. The file to be converted can not be open in another application during

conversion or an error will occur.

n time(s) Vout(V) Current(mA)

0 5.62E+08 3.280272 0.06258928

1 5.62E+08 3.280272 0.06258928

2 5.62E+08 3.280272 0.06258928

3 5.62E+08 3.280272 0.06258928

n m/d/yr hr:min:s ms time(s) Vout(V) Current(mA)

0 10/20/2017 20:42:08 437.286 5.62E+08 3.280272 0.06258928

1 10/20/2017 20:42:08 467.285 5.62E+08 3.280272 0.06258928

2 10/20/2017 20:42:08 498.261 5.62E+08 3.280272 0.06258928

3 10/20/2017 20:42:08 531.281 5.62E+08 3.280272 0.06258928

Rev1.3 128

VBG value

The value shown in this box is used to calibrate analog measurements, such as strain gauge, current sense,

or differential amplifier measurements. The value is measured from a high precision band gap reference

voltage on the USBID board. Whenever an analog measurement is made, band gap reference voltage is

measured and the calibration value in this box is updated. This value cannot be modified by the user.

Read VBG- This button allows you to read the current value of the calibration value.

Rev1.3 129

Current Sense Calibration

Current sense instruments require calibration. Without calibration, measured current values may have an

error of up to 10%. When calibrated, accuracy should be 0.5% or better. Two values require calibration:

Voffset, and G multiplier.

Calibration should be performed for Voffset and Gmultiplier whenever a sense resistor is changed or a

new current sense device is used. All current sense devices have unique calibration values of Voffset and

Gmultiplier, dependent both on device and current sense resistor (Rsense). Each device will have unique

calibration values for each value of Rsense used.

Maximum resolution is 0.03% of full scale range (range defined by sense resistor). Maximum accuracy is

0.04% but is dependent on the resolution of measurement of the sense resistor, load resistor used for

calibration, and voltage across load resistor. When calibrated, accuracy should be 0.5% or better.

Measure Voffset

With USBID not connected to USB cable:

Attach current sense instrument board to USBID with flat flexible cable.

Attach sense resistor (Rs) across sense resistor terminals (labeled Rsense on current sense board).

Leave Vout open (no load attached across Vout).

With power supply off, attach power supply leads to voltage input terminals, Vin and Gnd.

Polarity must be correct or current sense device and USBID may be damaged.

Connect USBID to PC with USB cable.

Start USBID software.

Turn power supply on. External power should never be applied to Vin when current sense device is not

attached to USBID and USBID is not being powered by USB cable.

In USBID software:

Click Real Time radio button in Acquisition Control box. Set Values Averaged/S to 2000. Set Plot

Length(S) to 100.

Set Sense Resistor to 1(actual sense resistor value is not used for this calculation).

Set Voffset(mv) to 0

Set G multiplier to 1

Push START in Acquisition Control box and acquire at least one full trace.

Push STOP in Acquisition Control box.

Rev1.3 130

Save data displayed by pushing Save Current Data button. Location and file name of saved data

will be shown in Data File text box.

In a spreadsheet open the saved data file. Calculate the mean value of the column Current(mA). This is

the value of Voffset(mv) for your device with the attached current sense resistor.

Enter this value in Voffset(mV).

Enter the actual value of the sense resistor in the Sense Resistor(Ohms) box.

In Save/Open Config box push Save As... button. Enter a file name for the configuration in the dialog box

and save the configuration.

Measure G multiplier

G multiplier is a correction factor for the gain of the current sense amplifier. Typically, the gain of the

device is within 0.2% of the nominal value. If this precision is sufficient Gmultiplier can be set to 1 (with

G multiplier=1 measured current will be within 0.2% of actual value). Fremont Instruments recommends

that G multiplier should be set to 1 for Rsense less than 100 Ohm.

If higher precision is desired a very good multimeter is required to measure the value of the sense resistor,

load resistor, and voltage across load resistor.

This measurement requires a known load resistor. The load resistor(Rl) should be much larger than the

sense resistor, by at least the factor of the gain for the current sense board. For example, if the sense

resistor is 1kOhm and the current sense board gain is 100, the load resistor should be at least 100kOhm or

greater.

Measurement:

Measure resistance of load resistor (R1) when not attached to current sense board.

Measure resistance of sense resistor (Rsense) when not attached to current sense board.

With USBID not connected to USB and power supply off.

Connect sense resistor across Rsense.

Connect load resistor, R1, across Vout.

Connect USBID to USB.

Turn on power supply.

With a multimeter measure the voltage across load resistor at Vout. The value measured is Vl.

Start USBID software.

Rev1.3 131

In USBID software enter Voffset (measured previously), enter sense resistor (Rsense), set

Gmultipier=1.

Select Real Time radio button in Acquisition Control box

Click START

Collect data for at least one full trace

Click STOP

Save data with Save Current Data button

Open data file shown in Data File text box

Calculate average value of Current(mA) column. Divide this value by 1000 since it is in mA and

you want the value in amps. This value is Iave.

Calculate the current across the load resistance(Il).

Il=Vl/Rl

Gmultiplier is then given by

Gmultiplier=Iave/Il

Enter value calculated above for Gmultiplier in Gmultiplier box in USBID software and save

configuration in Save/Open Config box by pushing Save As... button.

NOTE: To collect data with a higher number of averages, click Measure mAh radio button in

Current Sense control box and check Log Data box.

Rev1.3 132

Examples

Four examples are shown below. The first example is measurement of current through a resistor network

showing a current step. The second example shows a current measurement of a USBID with no

instrument board attached. The third example shows a current measurement of a USBID with an

accelerometer board attached during a waveform acquisition. The fourth example is a mAh measurement

and explains how to make a battery life calculation.

Example 1- Current is measured across the resistor network shown in Fig. CS16. The network is a 511kΩ

nominal resistor in parallel with a 149.4kΩ nominal resistor in series with a push button switch. The

current sense resistor is 498.5Ω. With a multimeter, the measured resistance of the network is 510kOhm

with the switch open and 115.5kOhm with the switch pressed.

Fig. CS16. Resistance network used to produce current step.

Fig. CS17 below shows the current measured when the switch is alternately pressed and released. Voltage

at Vout is measured with a multimeter when the switch is open and when it is closed. With the measured

resistance values, the actual current through the circuit can be calculated and compared with the value

measured by the Current Sense instrument.

Vout

switch

149.4kΩ 511kΩ

gnd

Rev1.3 133

Fig. CS17. Current through the resistance network described above when the switch is pressed and

released.

The calculated current step with voltages measured across Vout and the measured values of the resistor

network is 22.117uA. The value measured with the Current Sense instrument is 22.122uA, a difference of

0.02%.

Rev1.3 134

Example 1a- This example shows a 500nA step with 1nA resolution. This type of measurement can be

used to measure the quiescent current of components with nA resolution. In this example the sense

resistor is 23.24kΩ, giving a 1.35uA range. During the measurement the load resistance is toggled

between 3MΩ and 6MΩ resulting in a 544 nA step. This is shown below in Fig. CS17a.

Fig. CS17a. Current through a resistance network when the resistance is toggled between 3MΩ and

6MΩ.

Rev1.3 135

The figures below show resolution of the data above in Fig. CS17a. Both data sets are for the measured

current through a 6MΩ resistor. Both data sets use Waveform acquisition in the Acquisition Control box.

The difference between the two data sets is that the first uses Averaging set in the Acquisition Rate Set by

box and the second uses Clock set in the same box.

Current Through a 6Mohm Resistor With ~3.3V Supply Voltage

Acquisition Rate set by Averaging, 6S/s, 4000values averaged/Sample

546

547

548

549

550

551

552

553

0 2 4 6 8 10 12 14 16

Time(s)

Curr

ent(

nA

)

Fig. CS17b. Current through a 6MΩ resistor using averaging showing 0.3nA resolution.

The data shown below in Fig.CS17c has been made through the same 6MΩ load resistor used above but

data is acquired at the maximum rate, 9.8kS/s, with no averaging. Peak to Peak value is less then 6nA and

standard deviation is 1nA.

Current Through a 6Mohm Resistor With ~3.3V Supply Voltage

Acquisition Rate 9813S/s

546

547

548

549

550

551

552

553

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05

Time(s)

Curr

ent(

nA

)

Fig. CS17c. Current through a 6MΩ resistor with no averaging.

.

Rev1.3 136

Example 2- This example shows a current measurement of a USBID with no instrument board attached.

The variation in current shown below in Fig.CS18 is due to the LED blinking on the USBID board.

Current through the LED is approximately 4mA.

Fig. CS18. Current through the USBID with no instrument board attached.

Rev1.3 137

Example 3- This example shows a current measurement of the USBID with an accelerometer instrument

board attached while a measurement is being made. The variation in current shown below in Fig. CS19 is

due to both power consumption of the LED blinking on the USBID board and additional power consumed

by the microcontroller during a measurement (point number 22-72). While the measurement is being

made the LED is turned on so additional current to the USBID during the measurement is the difference

between the current for points 22-72 in the plot and current of the peaks in point number 0-21.

Fig. CS19. Current measurement of the USBID with an accelerometer instrument board attached while a

measurement is being made.

Rev1.3 138

The plot below, Fig.CS20, shows a summary of the previous two examples. Two waveforms are plotted:

current through the USBID when no accelerometer instrument board is attached, and current through the

USBID when an accelerometer is attached and a measurement is made.

Fig. CS20. Current measurement of the USBID with an accelerometer instrument board attached while a

measurement is being made compared with a USBID current measurement when no accelerometer is

attached.

From the data in this plot the current through the USBID can be determined when no instrument is

attached, when an accelerometer instrument is attached, and the current while an accelerometer is attached

and a measurement made.

The average current through the USBID with no device attached is 16.8mA, from an average of the

waveform labeled USBID in the above plot.

The current through the accelerometer instrument board can be determined by the difference in the

minimums of the waveforms USBID and USBID+Acc(Accelerometer Current). This difference is the

current through the accelerometer, approximately 300μA.

Current comparison of the USBID with no accelerometer attached, and

accelerometer attached during a measurement

14

15

16

17

18

19

20

21

22

23

0 10 20 30 40 50 60 70 80 90 100

Measurement number

Cu

rre

nt(

mA

)

USBID

USBID+Acc

Accelerometer measurement

Accelerometer

Current

Increased

USBID

Current During

Measurement

Rev1.3 139

During the Accelerometer measurement the current through the USBID increases because of increased

demands on the USBID microcontroller from communication with the accelerometer instrument board.

This is shown in the plot above as Increased USBID Current During Measurement, approximately 2.6mA.

Example 4- This is an example of a Statistics acquisition and also shows a battery life calculation. The

current through the resistor network described in example 1 is measured with statistics calculated and data

logged to the PC. Fig. CS21 shows the current through the resistor network when the switch is pressed

and released.

Fig. CS21 Current through the resistance network when the switch is pressed and released.

The plot below, Fig. CS22, shows the saved data from the plot above.

Rev1.3 140

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 50 100 150 200 250 300

Time(s)

Curr

ent(

mA

)

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

mA

h

IAve(mA)

mAhFromStart

Fig. CS22 Current through the resistance network when the switch is pressed and released with mAh also

plotted.

Battery Life Calculation

To calculate battery life from the data in the figure above, first determine the average current, Currentave,

for the 303s measurement time. This will just be the mAh value at 303s divided by the hour equivalent of

303s.

The mAh value at 303s is 0.001407mAh.

The measurement time in hours is 303s/3600s/h = 0.0842h.

From the two above values Currentave can be calculated.

mAh

mAhCurrentave 016708.0

0842.0

001407.0==

For a battery rated for 200 mAh, typical for a 2032 lithium ion battery, the life expectancy of the battery

when cycled as shown in the above figure will be BatteryLife:

weekshmA

mAheBatteryLif 7111971

016708.0

200===

Selecting a Sense Resistor

Rev1.3 141

A sense resistor should be smaller than the resistance (χ) of the device being measured, at least by the gain

of the Current Sense instrument board plus 5%. To be in measurement range, the value of a sense resistor

(Rsense) for a current sense board with gain G will have a maximum value of

05.1*G

Rsense

= F1

For example, if the Current Sense board has a gain (G) of 100 and the impedance (χ) of the device being

measured is 52400Ω, a sense resistor value that will produce an output at the maximum measured range

will be

=== 49905.1*100

52400

05.1*GRsense

F2

If the impedance(resistance) of the device attached across the output terminals is known the value of the

sense resistor, Rsense, can be calculated to give an output at a desired level of the range (RangeLevel).

05.1*

*

G

RangeLevelRsense

= F3

RangeLevel is the fraction of the allowed range, a value between 0 and 1. If you want to set the current

value measured to the midpoint of the range, set RangeLevel = 0.5. For example, if the Current Sense

board has a gain (G) of 100 and the impedance (χ) of the device being measured is 52400Ω, Rsense is

calculated as

=

== 5.24905.1*100

5.0*52400

05.1*

*

G

RangeLevelRsense

F4

Impedance of a solid state device is hard to measure so if you do not know its nominal impedance, my

recommendation is to start with a small value of Rsense. Make a measurement. If the measurement is

above midrange, decrease Rsense. If the measurement is below midrange, increase Rsense. The formulas

given above can help to find a desirable value of Rsense.

WHEN Rsense IS CHANGED, ALWAYS ENTER THE VALUE OF THE CURRENT SENSE

RESISTOR (Rsense) IN THE BOX LABELED Sense Resistor(Ohms) IN Analog Acquisition Parameters

BEFORE THE START OF A MEASUREMENT. THE USBID DOES NOT MEASURE THIS VALUE

AND IT MUST BE ENTERED MANUALLY. IF YOU WANT THIS VALUE TO BE USED AS THE

DEFAULT, USE THE Save/Open Config BOX AND SAVE AS Config_0.

The three examples below show current out of range, current just in range, and current at middle range.

All three measurements are made with the Real Time button checked in Acquisition Control.

Rev1.3 142

Example5- The first example shows current out of range. Fig. CS23, is for a 499Ω sense resistor with a

499Ω load resistor.

Fig. CS23. Current measurement when the current is out of range.

Rev1.3 143

Example6- The second example shows a plot of data when current is just barely within range. Fig. CS24,

is for a 499Ω sense resistor with a 52.4kΩ load resistor across Vout. This is the value calculated above in

formula F2 for the load impedance for current to be in range.

Fig. CS24. Current is just within range.

In the above plot, the current measured with the Current Sense instrument is 62.605uA. The current

measured with a multimeter through the load resistor is 62.63uA, a difference of 0.045%.

For the current to be in the middle range for a 52.4kΩ load impedance, the sense resistor value needs to be

reduced by a factor of 2 to approximately 250Ω. This is shown in the example below.

Rev1.3 144

Example7- The third example shows a plot of data when the sense resistor has been chosen to set the

measured current to middle range. The load resistance is the same as that used in the previous example,

52.4kΩ, but the sense resistor has been reduced by a factor of 2 to 249.4Ω, as calculated with formulas

F3,F4 given above.

Fig. CS25, is for a 249.4Ω sense resistor with a 52.4kΩ load resistor across Vout.

Fig. CS24. Current is at the middle range for measured device impedance 52.4kΩ, Rsense 249.4Ω..

Rev1.3 145

Maximum Plotted CurrentValue

The maximum plotted current value is the maximum current that can be measured by the current sense

instrument. This is dependent on the sense resistor and gain of the current sense instrument board. The

choice of a sense resistor must be based on the gain of the current sense instrument board and the

impedance (resistance) of the device attached to the output terminals of the current sense instrument

board. See the discussion above in the section Selecting a Sense Resistor.

The Current Sense board puts out a voltage proportional to the voltage it measures across Rsense scaled

by the gain G. For example, if the Current sense board measures a drop of 0.01V across Rsense and the

gain of the Current Sense board is 100, the voltage output to the USBID will be V=0.01V*100=1V. This

voltage is measured by the USBID and reported to the PC program. The PC program then calculates the

actual current based on Rsense, G, Voffset, and G multiplier.

The maximum value of plotted current is based on the maximum voltage value from the Current Sense

board the USBID will be able to measure. The maximum value of this voltage is 3.3V. This is also the

maximum voltage that can be read by the USBID.

The maximum current value plotted in mA, I(mA), is then

senseRG

VmAI

*

95.0*1000*3.3)( =

The value of 3.3V is the nominal value of the USBID voltage. The value of 0.95 is a scale factor to reduce

the maximum plot value so that the plotted values will be 5% away from the upper rail(max voltage,3.3V)

to ensure linearity and avoid saturation. This value of 0.95 was also chosen to compensate for the

tolerance of the 3.3V voltage regulator(2%). The value of 1000 converts amps to milliamps.

Rev1.3 146

Specifications

Electrical

Maximum current: 1A

Dropout voltage at 1A: 250mV @ 25C, 275mV @ 75C

Supply voltage to current sense instrument board: 4.5V min, 15V max

Flat Flexible Cable


Width: 3.5mm (0.138”)

Length: 300mm (11.8”) as supplied with SG Instrument board




CS Instrument Board and USBID Board Physical Specifications (nominal)


Current Sense Board

Mass: 5.33g


1.00 (25.4)

1.25 (31.75)

0.125 (3.17)

1.10 (27.94)

0.40 (10.16)

Rev1.3 147

USBID Board

Mass: 2.35g


0.75 (12.7)

1.00 (25.4)

0.125 (3.17)

.080 (20.32)

0.125

(3.17) (10.

16)

Rev1.3 148

7. Accessories

Instrument Board Mount

The instrument board mount is a platform that can be used to securely attach the USBID board and

instrument boards. It can be used to mount one USBID board and one instrument board.

FFC Cables

The flat flexible cables (FFC) available from Fremont Instruments come in a variety of lengths from

80mm to 1000mm. Pins have a pitch of 0.5mm with contacts on the top of the cable at both ends. Cable

suppliers call this either “forward direction” or “top on both sides, backers on both sides”. Cable lengths

available from Fremont are 80mm, 300mm, and 1000mm.

Accelerometer Calibration Block

This block can be used to calibrate accelerometers. It is an easy way to align an accelerometer to the

orthogonal axes required for calibration using the USBID software. The overall nominal block

dimensions are 1.750” X 1.000” X 0.500”.

Micro USB Cable

The USBID requires a micro USB cable for the interface between your PC and the USBID board. Cable

lengths available from Fremont are 1 meter, 2 meter, and 5 meter.

Rev1.3 149

8. USBID and Instrument Board Care and Handling

Static electricity can damage or destroy your instrument boards. Fremont boards are sensitive to static

electricity so care should be taken to avoid a discharge of static electricity to the board or a discharge

nearby.

Boards may have exposed contacts on their bottom surfaces so boards should never be placed on a

conductive surface with power applied to the board as these contacts could be shorted resulting in damage

to your board.

FFC cables have a limited number of insertion/removal cycles. Depending on care taken care during

insertion and removal this can be several hundred cycles. However, after multiple insertions the contacts

on the cable may delaminate, resulting in adjacent conductors in the cable being shorted. This could

damage your boards. Before FFC insertion always closely examine the contacts on your FFC to see if

delamination has occurred, requiring cable replacement.

Flat Flexible Cable (FFC) connectors also have a limited number of insertion/removal cycles. Connectors

have been tested up to 500 insertions with the connector still functional. However, the manufacturer of the

connector specifies significantly fewer insertion/removals. Insertion/removal cycles of a FFC from the

FFC connector should be minimized.

Rev1.3 150

9. External Call of USBID Software

The USBID software can be called by an external program and all the functionality of the USBID

software can be accessed by this external program.

This functionality will be enabled if there is a demand for it.

USB Instrument Driver and Instrument ... - Fremont Instruments

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