DIGITAL MWL TIMETER er - Conrad · l 4. A/D CONVERTER DESCRIPTION FEATURES q 40,000 Count...

DIGITAL MWL TIMETER

e r

C O N T E N T S

SECTION PAGE

1.

2.

3.

4.

5.

6.

7.

8.

10.

11.

12.

INTRODUCTIoN .................................................. 1

SpEClFlCATl(-JN .................................................. 2

BLOCK DIAGRAM ................................................ 6

A/D CONVERTER DESCRlPTlON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

FUNCTIONAL CIRCUIT DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5-1. DC/AC VOLTAGE MEASUREMENT CIRCUIT

5-2. CURRENT MEASUREMENT CIRCUIT

5-3. RESISTANCE MEASUREMENT CIRCUIT

5-4. DIODE & AUDIBLE CONTINUITY TEST CIRCUIT

5-5. TEMPERATURE MEASUREMENT CIRCUIT

5-6. WRONG POSITION DETECTOR & WARNING BEEP CIRCUIT

5-7. AUTO POWER OFF CIRCUIT

5-8. CAPACITANCE MEASUREMENT CIRCUIT

5-9. FREQUENCY MEASUREMENT CIRCUIT

5-10. INDUCTANCE MEASUREMENT CIRCUIT

5-l 1. DUTY MEASUREMENT CIRCUIT

PERFORMANCE TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . 33

PCB LAYOUT & COMPONENTS ARRANGEMENTS -. . . + -. . - - - -. . -. . . 35

10-l. LCD LAYOUT

SCHEMATIC DIAGRAM . . . . . . . . . . . . _. . . . . . . . . . . . . . . _ _ . . . . . . . . . . . . . 38

PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..I. 42

General

Maximum Voltage between anyTerminal and Earth Ground

Input Impedance

Fuse Protection

?

Display (LCD)

Digital

Analog

Frequency

Backlight

Meter Operaing Temperature

Temperature forquaranteed accuracy

Meter Storage Temperature

Relative Humidty

Battery Type

Battery Life

Size (H x W x L)Meter only:

Weight Meter Only:

Safety Meter:

5oov.

10 !& (nominal) < 100 pF

0.8A 250V FAST FUSE 1R 35A20A 25OV FAST FUSE 1R 15OOA

Counts : 4,00019,999 in Frequency range

41 SegmentsUpdate Rate : 4/set

Counts : 19,999Update Rate : l/set @ > 10 Hz

Backlight turns on for 60 secons, then turns off automaticallyif not turned off by user.

0°C to 40°C ( 32°F to 104°F 1

23=C t 5°C ( 73’F * 9°F i

-10°C to 5O’C ( 14°F to 122’F

0% to 75% ( 0 “c to 35 “C ; 32°F to 95’F 10% to 70% ( 35°C to 50°C; 95°F to 122°F )

9V, NEDA 1604 or 6F22 or 006P

200 hours typical with alkaline

3 9/16 in x 7 7/16 in x 1 l/2 in(90 mm x 189 mm x 38 mm)

12 7/8 oz. (3649)

Designed to Class II per IEC 1010and UL 1244

l

4. A/D CONVERTER DESCRIPTION

FEATURES

q 40,000 Count Resolut ion

II 0 . 0 2 5 % A c c u r a c y

0 2 0 C o n v e r s i o n s p e r S e c o n d

o M i c r o p r o c e s s o r I n t e r f a c e

0 1004 O p e r a t i n g S u p p l y C u r r e n t

q Low Externa l Component Count

0 5fiv R e s o l u t i o n

q Demonstrat ion Kit Aval iable

MAX134/DEMO

GENERAL DESCRIPTION

The MAX133 and MAX134 are in tegra t ing A/D conver te rs fo r 3% digi t

multimeters and data acquisition systems such as data loggers and weigh scales, The

A/D’s internal resolution is *40,000 counts. An extra digit is supplied as a quard digit to

allow autozero or tare of a 4000 count displayed reading to l/10 of a dispalyed count.

The conversion time is 50ms.

The MAX133 and MAX134 differ only in their microprocessor interface. The

MAX133 has a 4 bit multiplexed address/data bus while the MAX134 has 3 separate

address lines and a 4 bit bidirectional data bus. Both devices can be used with 4, 8,

and 16 bit microprocessors.

When controlled by a microprocessor, the MAX133 and MAX1 34 can perform

auto-ranging measurements from *400.0mV to *4OOOV ful l scale. External attenuator

resistors are required, but range switching is performed by the A/D.

The power supply is typical ly a 9V battery or *5V. Opera t ing cur rent i s

typically 1004 while standby current in only 254.

7

.

SYSTEM CONSIDERATIONS

The MAX133/134 is intended for use with a microprocessor. The MAX133/134

contains an A/D and auxiliary circuitry such as attenuator range switches, a piezoelectric

beeper driver, an active filter, a low battery detector, and both analog and digital power

supplies; but it does not include any display drive capability. The MAX133/134 reduces the

component count and system cost by minimizing the external components required for the

analog portion of the system, but does not restrict final product features by including

autoranging or other digital control functions. The MAX133/134 is intended to work as the

analog front end of a microprocessor, with the features of the end product being

determined by the microprocessor software. Table 1 shows how the execution of several

typical functions is partitioned between the MAX133/134 and the microprocessor.

The MAX133/134 provides all of the logic and counters for control of the

conversion sequence, and the external microprocessor does not have to perform any

critical timing or complex control of the MAX1 33/l 34. The MAX133/134 has range switches

for a 5 decade attenuator which uses external resistors, and has additional mode-selection

circuitry for performing voltage, current, AC or DC, ohms, and continuity measurements.

The 5 decade attenuator and mode-selection circuitry is Icontrolled by an exeternal micro-

processor via control bits written inio the MAX133/134.

The MAXl33/134 has normal mode rejection of line frequency of at least 80dB on

the voltage ranges; the microprocessor selects rejection of either 5OHz or 60Hz by setting

a MAX133/134 control bit. A two pole active filter can also be turned on by the micro-

processor, adding about 40 dB normal mode rejection above !%Hz. See the “Digital

Interface” section for details on which functions can be controlled by the external micro-

processor.

The basic blocks of the MAX1 33/l 34 are

A/D section

Input Range Swiching

Ohms Circuitry

Active Filter

Power Supply, Common, Low Battery Detector

Oscillator and Beeper Driver

Digital Interface

10

obtain a zero-corrected reading. The zero correction that must be subtracted is determined

by the MAX133/134’s internal offsets. Since these offsets are relatively slow changing, zero

conversion readings need only be taken offen enough to track long term drifts andtemperature changes. The zero conversion reading will change slightly with a change in

common mode input voltage or reference voltage, and a new zero conversion readingshould be taken if either of these change.

In ratiometric ohms measurement the reference voltage will change significantly

as the value of the unknown resistor varies To reduce the errors caused by the system

offset the MAX133/134 “chops” the input buffer and integrator. The “chop” consists of areversal of the input transistors during the conversion cycle. The timing of this chop is

such that in the R/2 or ohms measurement mode, the system offset is almost completely

nulled out if the X2 mode is not selected. Even if the X2 mode is selected, the system

offset does not exceed 5000 counts on any range. Since the internal full scale range of

the MAX133/134 is greater than +49,000 counts, at least~:40,000 counts of resolution are-available after zero offset correction.

Each conversion result is latched into a Conversion Register which can be readby the microprocessor. The data format is nines complement BCD (a zero reading is

00000, a -1 reading is 99999, a -25000 reading is 75000). The nines complement form isthe most convenient BCD format since the addition of the nines complement of a number

is equivalent to subtracting that number. See “Software Notes” for simple BCD to binary

conversion algorithms.

The last digit of conversion is used for digital autozero and is usually not

displayed. Note that each count of the least significant digit of the MAXl33/134 output

corresponds to l/10 of a count if a 4000 count full scale display is used. For current

ranges with a voltage drop of only 200mV, the measured reading can be multiplied by two

by using the X2 (“times 2”) function of the MAX133/134. The X2 function reduces the RN

resistor value by a factor of two during the Integrate phase. With the X2 range, a 200mV

input voltage will result in a full ‘scale, 4000.0 measured reading Alternatively, ‘the normal

400mV range can be used, wi th the multiplication by two being done by the

microprocessor digitally. In this case, each count of the least Significant digit iS t/5 Of a

displayed count. A 100mV full scale voltage drop can be achieved by using both the

MAX1331134 X2 range and a digital times 2 multiplication in the microprocessor.

Each of the 20 conversions per second has a Zero Integrator phase to ensurerapid recovery from overload, and the MAX133/134 will recover to within 2 counts oneconversion after an overload of 10 times full scale when the onboard active filter is not

used.

13

.

2) INPUT RANGE SWITCHING

In voltage measurement ranges other than 4OOmV, voltages are applied to thepin labelecl 10M Sz through a 1 OM Q resistor. By selecting the proper shunt resistors (1 .l M

Q through 1 KQ) the input voltage will be attenuated to a 4OOmV range. The input

attenuator switch section includes analog switches to switch both the input current and to

sense the voltage on the shunt resistor. Other input switching functions select between the

output of the input attenuator and the voltage developed across the current sensing

resistors during current measurement. See Figure 3.

The 5pA input bias current of the MAXl33/134 might result in unacceptableerrors with a 10MQ input resistor on the 400mV scale, so a separate pin with a 700kS2

to 1 MS2 input resistor is used for the 400mV scale. The IOM 52 resistor used on the

higher voltage ranges does not cause appreciable error since the input leakage current is

-shunted to ground through the 1 .l 1 MQ to 1 kQ attenuator shunt resistors.

To avoid errors that might occur through coupling of high frequency, highvoltage signals from the input of the attenuator to the low level 400mV and Current inputs,

these two inputs have 10kQ switches which connect them to Common whenever they are

not selected.

The input section also includes switches to allow an external AC-DC converter

to be inserted into the signal path.

3) OHMS AND DIODE MEASUREMENT

The input attenuator resistors are also used as reference resistors in the ohms

mode. Note that the IOMQ resistor must be externally paralleled with the other resistorsto get exactly 1 M 52, lOOk52, etc. The ohms source buffer input is usually-connected

directly to the external bandgap reference or to another 1.25V source. In the 4kQ through40MQ ranges there will be a total of 1.25V across the series combination of reference

resistor, unknown resistor, and the input protection network; and the maximum voltage

across the unknown resistor at full scale will be less than 4OOmV. On the 4OOS2 range,the ohms voltage source is a diode connected to V+ through a 2kS2 p-channel switch.With a 3V Common voltage, this supplies approximately 2.2V across the series

combination of reference resistor, unknown resistor, and input protection network. This

higher voltage is used on ths 4CQQ range to compensate for the decrease in reference

voltage caused by the input protection network. The MAX133/134 are designed to operate

with PTC protection resistors of 2kQ or less.

14

A 1kQ reference resistor is used for the 4OOQ full scale, a IOkSZ reference fora 4kQ full scale, etc. A IOMQ reference resistor is used for both the 4M 52 full scale and

the 40MQ full scale. To get the correct results in the ohms measurement or R/2 mode,the conversion result must be multiplied by two either digitally by the microprocessor or by

using the X2 range. except on the 40MQ scale. The 40MQ range has the same

reference resistor as the 4M Q range but a times 10 scale factor Is obtained by not

multiplying by 2, and by activating the S5 tunction. If the times 2 multiplication is

performed by the microprocessor, the Read Zero offset ot the MAX133/134 in the ohrns

mode wiil be Just a few counts, and will be nearly independent of the value of the

unknown rssistor being measured. If the

then frequent Read Zero readings should

proportional to the reference voltage, and

the unknown resistor varies.

MAX1 33/134 X2 mode is used to multiply by 2,

be taken. since the read zero offset is inversely

the reference voltage varies as the resistance of

-Since the input protection PTC resistor shown in Figure 4 reduces the reference

and input voltage, particularly on the 4OOQ scale, the PTC resistance should be as lowas is possible while maintaining the desired level of protection. Greater than 2kQ PTC

resistancs will increase the noise lsvel ot meaourements on the 4OOQ range.

Since the MAX133/134 does not use a reference capacitor, the only limit on the

response time in the ohms mode is the active filter. Even when the active filter is turned

off, RFILTER! is still connected, and the input voltage must charge the filter capacitors. This

will generally be noticed only on the 4MQ and 40M 52 ranges.

A diode test range can be implemented by simply connscting to V+ the PTC

used for input protection in the ohms ranges. The PTC then delivers approximately 1mA

of current to the diode. The diode voltage can be measured either on the standard 4V

scale, or on the 4OOmV scale with the i5 function activated to result in a 2V full scale.

As always, the latched continuity circuit is active, and it will latch whenever the input-.voltage goes beiow approximately 1OOmV. The microprocessor can also test the measuredvoltage at the end of each conversion if a more precise detection of continuity threshold

is desired.

16

.

4) ACTIVE FILTER

The 2 pole active filter circuit is shown in Figure 5. The opamp’s offset hss noeffect on the DC accuracy since the opamp is only AC coupled and the DC signal pathis only through the passive 1 MQ resistor. Note that the active filter will limit the speed ofresponse of the MAX133/134 to input voltage changes, and for that reason it may bedesirable to disconnect the input filter during autoranging. Since the atthe filter input varies with the input attsnuator selected, the response

on the 4V range.

source impedancetime will be slower

5) OSCILLATOR AND BEPPER DRIVER

The MAX133/134 is designed to operate with a 32768Hz tuning fork crystal

similar to the Statek CX-IV, using only one external capacitor and no external resistors. If

desired, the MAX133/134’s OSC IN pin can be driven externally.

The 32kHz clock is used internally as the clock for the sequence and

measurement counters. The 32kHz clock is also divided down to 2048Hz and 4096Hz fordriving a beeper. The beeper output swings from V+ to V- and can directly drive

piezoelectric beepers. Two controi bits set by the microprocessor select the frequency

(2048 or 4096 Hz) of the beeper and turn it on or off. Since the beeper is controlled by

the microprocessor, it can be used for both continuity indication and for an audibleoperator feedback signal for peak hold or range changes.

6) POWER SUPPLY:

COMMON, DIGITAL GROUND, LOW BATTERY DETECTOR-

Both the MAX133 and MAX134 can operate from either a nominal 9V battery or

a +5V supply. The maximum power supply current in DC voltage and DC current modes

is 250& with a typical operating current of lOOti.

Analog Common is derived from a zener and is nominally 3.OV below V+. Forlowest cost applications the Common voltage, with a tempco of SOppm/‘C, may be usable

as a reference. In most applications, a bandgap reference wiil be connected to Common,with a pullup resistor to V+, and a voitage divider connected across the bandgap

reference to generate the 545mV (60Hz operation) or 655 (50 Hz ope ation) reference

voitage. In a battery powered meter, the Analog Common pin is used as the system

ground reference point.

17

COMPONENT SELECTION

1) INTEGRATION RESISTORS

For an accurate times 2 multication in the X2 mode, the two RINT resistors must

be exactly equal. If the X2 mode is not needed, then connect a 604kQ RJNTI between

Buffer Out1 and the integration capacitor CM, and leave Buffer Out2 open. The value of

both RINTI and RINT2 is nirmally 301 kS2 for a 545mV or 655mV reference. This sets the

integratoe output current to 2@ during the Deintegrate phase. If the reference voltage is

different, scale the R INT resistors proportionately. -

1) INTEGRATION CAPACITOR

The normal va lue fo r the in tegra t ion capac i to r i s 4.7nF. Th is va lue , in

combination with the integrator output currsnt and the clock frequency sets the integrator

swing to about 3V for the voltsge ranges when RIMI = RINQ = 301 kS2 and the c lockfrequency is 32,768Hz. While the same integrator swing can be achieved with other values

of capacitors by changing the value of RINT, lower values of CINT may introduce more

noise through increased pickup ot noise and 50/60Hz signals. Excessiveiy high values ot

Clm will also cause noise problems by reducing the integrator swing to unacceptably low

values, causing the comparator noise to dominate the conversion errors. Large values of

GIN wili also cause linea-ity errors since the settling time of the internal times 10 circuitry

is affected by the value of CWT.

The dielectric absorption of the integration capacitor directly aftects the integral

Ilnearity, and high quslity polypropylene capacitors aie recommended. PO&carbonate and

polystyrene capacitors may give satisfactory performance in less demanding applications,

while the fourth choice, polyester (MylarTM), will cause about 0.1% integral non-linearity.

2) ACTIVE FILTER COMPONENTS

The RC time constant of the active filter components sets the rolloff frequency

of the filter. The etfective value of the RFILTE&Figure 5) is the sum of its value plus the

source impedance driving the filter. In the 30V range for example, the effective source

impedance is the 101 kQ resistor in the attenuator. In the 3V range, the sffective source

impedance is 1 MS2. This variable source impedance will alter the tilter characteristics

samewhat as the different voltage ranges are selscted. The effect of the different sourceimpedances can be minimized by increasing the value of the f i l ter res is to rs wh i le

decreasing the value of the tiltsr capacitors proportionately. This, however, will increase theoffset error caused by the A/D input leakage current flowing through the filter resistors. For

-

19

most applications. filter resistor values between 1 M Q and 3MQ are optimal.

The RC time constant sets the filter roiloff frequency. A low rollott frequency

improves the normal mode rejection, but at the expense of a longer settling time in

response to input voltage step changes. Another consideration when an LCO bargraph is

used is aliasing. If the bargraph is updated at 20 times per second and there is a 19Hzcomponent in the signal being measured, the beat frequency of 1Hz will appear on the

LCD bargraph dispisy. To avoid aliasing effects, the filter time constant is normally set to

less than 10Hz. A 3Hz roiloff (RC = 4Oms) further reducss the a l ias ing ef fects and-increases normal mode rsjection while still maintaining an acceptable transient response

with fast varying signals.

Dielectric absorption in the filter capacitors will create a smail, long time constant

settling error; therefore polypropylene capacitors are recommended.

3) CRYSTAL, AND CRYSTAL OSCILLATOR CAPACITOR

The MAX133/134 oscillator is designed to use high Q, low power 32.768Hz

crystals such as the Statek CX-1V. The series resistance should be less than 30kS2.

The oscillator capacitor connectsd to Osc Out is typically lOpF, but should be

adjusted to optimize perlormance with the chosen crystal. If overtone oscillations are

observed, then increase the value ot the oscillator capacitor. It on the other hsnd, the

oscillator has start-up problems. then reduce or eliminate the oscillator capacitor. Keep the

stray capacitance across the crystal to a minimum since excessive stray capecitance will

prevent oscillation.

4) ATTENUATOR NETWORK

The attenuator network and the associated range selection

in Figure 3. If the resistance of the internal range selection switches

theoretically ideal values for the attenuator network would be 10M Q,Q, lO.OlkQ a n d l.OOOlkQ.

switches are shown

were OQ , then the

l.llllMQ, lOl.lOlk

The voltage coefficient of the 1OMSZ resistor should be as low ss possible,

since it will have high voltages applied to it in the 400V and 4,000V ranges. In addition,

the temperature coefficients of the various attenuator resistors should be as low a spractical since this affects the accuracy of the ohms measurements. The tsmperature

coefficients ot the attenuator resistors should track each other since the ratio of the-

resistor values sets the accuracy of the voltage measurements,

20

5) INPUT ATTENUATOR COMPENSATION CAPACITORS

The input attenuator is often compensated with low value capacitors to maintain

a constant attenuation ratio over a wide bandwith. The value of the compensation

capacitors should be as low as practical, otherwise the 10M 52, pin will be driven above

V+ or below V- when high frequency, high voltage signals are applied to the attenuator

input, causing gross conversion errors.

6) POSITIVE TEMPERATURE COEFFlClENT RESISTOR (PTC)-

As shown in Figure 4, a PTC is normally used as part of the protection circuit

in the ohms mode. Excessive values of PTC resistance, however, reduce the voltageacross the unknown and reference resistors. particularly on the 40052 range. PTC

resistances above 2kQ will degrade system performance by reducing the signal ievel on

the 4OOS2 range, thereby increasing the conversion noise. Values above 5kQ will cause

additional error since the voltage drop across the PTC appears at the A/D as a common

mode difterence between IN HI and Ref LO.

-

21

5. FUNCTIONAL CIRCUIT DESCRIPTION

5-1. DC/AC VOLTAGE MEASUREMENT CIRCUIT

The input voltage is first put through the voltage divider(Fig. A), where the divisionratio is selected by the range selector switch. The maximum output voltage from the

voltage divider is 200mV DC/AC. If the function switch is set to ACV, the output from the

voltage divider is switched to the AC/DC convet-ter(Fig. B). The output of the AC/DC

converter is the RMS of the AC input. The DC voltage is then applied to pins 38 and 39

of the MAX133/134 and is compared with the 1OOmV reference voltage applied to pins 43

and 44. The MAX133/134 then computes the resultant voltage and displays it by driving

the LCD display.

5-2. CURRENT MEASUREMENT CIRCUIT

A fused current shunt performs the current-to-voltage conversion required by the

MAX133/134 A/D converter. When the input current is DC, the IR drop is put through a

low-pass filter before being inputted to the A/D converter(MAX133/134) pins 38 and 39.

When the input current is AC, it is first processed through the AC/DC converter, and then

inputed to the A/D converter.

5-3. RESISTANCE MEASUREMENT CIRCUIT -

A ratio technique is used. When the function switch is set to OHM, a series circuit

is formed by the internal reference voltage, the selected reference resistor and theresistance to be measured. The ratio of the two resistors is equal to the ratio of their

respective voltage drops. Since the value of the reference resistor is known, the

MAX133/134 A/D converter calcurates the value of the unknown resistor as follows;

Reference Resistor V Drop through ReferenceWDl)=

Unknown Resistor V Drop through ReferenceWDx)

RI VDl-_=- (RX) (vD~)=(R~) nmx)Rx VDx

(Rl) (VDX)R x =

VDl

22

.

5-4. DIODE and AUDIBLE CONTINUITY TEST CIRCUIT

The diode under test is connected to the A/D converter and the forward voltage

drop is measured. Multivibrator is operated when the input resistance is less than 30 ohm

and frequency of 2kHz is applied to the buzzer through a buffer to sound.

5-5. TEMPERATURE MEASUREMENT CIRCUIT-

5-6. WRONG POSITION DETECTOR & WARNING BEEP CIRCUIT

This circuit consists in detector switch on PCB(D/SW), selector’s posit ion

switch(P/SW), comparator and oscillator. The D/SW, which is connected to with A and 10Ainput jack terminals, is turned ON when probe is inserted into A or 10A terminals. P/SW

is turned ON when the range selector poses on any other ranges except current

measurement ranges. The comparator compares the status of D/SW and P/SW andoperates the oscillator when both of them are ON. The oscillator then generates alarm

sound.

5-7. AUTO POWER OFF CIRCUIT

This circuit consist in CPU, TR, Capacitance, and

was about 15 minutes. Power has turn off automatically.

23

battery on PCB. If no reading

.

5-8. CAPACITANCE MEASUREMENT CIRCUIT

This circuit is for the display of capacitance value by measuring the charging/

discharging period of the unknown capacitor by the TR Q2, U3 and U8 which are

controlled by CPU.

5-9. FREQUENCY MEASUREMENT CIRCUIT -

This circuit displays the frequency value by the internal counter of Ul during

measuring the AC Voltage. The signal comes in, goes through the same divider as the

attenuator and the amplitude is to be fitted th the input of Ul via U3.

5-10. INDUCANCE MEASUREMENT CIRCUIT

5-l 1. DUTY MEASUREMENT CIRCUIT

24

. 7 . CALIBRATION

7- 1 S o f t w a r e Ca!ibration fr:;r 35X G3librat:m Ri~xxduie

SCAL350- I Cali bration

1. DCV calibration

- I n s e r t ES--232c CGbiP ?Q DMM.

- - IrT3W Tf?St i&3ds TC CjJR( & L’ ]J.$SltlQI-\.

- S e t t h e f u n c t i o n swtctr to the V rariye.

11 Input DC 3V and press 3V button of SCAL350- I.

2) Input DC 300V and press 300V button of SCAL350- I

3 ) Input DC 500V and press 5QW buttor, d SCAL350- I .

2. ACV calibration

- Insert RS-232C cable to DMM.

- Insert Test leads to COM & V position.

- Set the function switch to the V range.

li Input DC 3V and press 3V button of SCAL350- I

2) Inout A C 3 V witil 50H.z a n d 3V 60Hz b u t t o n of SCAL350- I .

3. A calibration


- lnscrt Test leads to C O M & V position.

- Set t h e functton sw~teh to the A ranyc.

1) Just press OA button of SCAL-- I .

21 lrqmt 2A and press 2A tUta !.li S C A L . 3 5 0 - I

3) tnput 2 A a n d p r e s s 0 2 A button af SCAL350- I

_ .” I_._ . . . .-. __ .“r___Cr -. _..--..,_... .1 _,” _.

SCAL3!50- II Calibration

1. ti Calibration

- Insert RS-23X cable to DMM.

- Insert Test leads to COM & ,dmA position.- Set the function switch to the fi range.

1) Just press O,VA button of SCAL350- II.

2) Input 2OO/_LA and press 200@ button of SCAL350-II.

3) input 2000,~A and press 2000,~A button of SCAL3509.

2. mA Calibration


- Insert Test leads to COM & ,&mA position.

- Set the function switch to the mA range.

1) Just press OITIA button of SCAL350- IT.

2) Input 201.1~4 and press 20mA button of SCAL350-II.

3) Input 2OOmA and press 2OOmA button of SCAL350-II.

3. Capacitance calibration

- insert RS-232C cable to DMM.

- Insert capacitor to Capacitance socket.

- Set the function switch to the CAP range.1) Input 46.5pF and press 47bF button of SCAL350- II.

2) Input 7OOti and press 7OOti button of SCAL350- II.

-.

27

SCAL3504I Calibration

7. mV Calibration


- Insert Test leads to COM & V position.- Set the function switch to the mV range.

1) Input 300mV and press 3OOmV button of SCAL350-III.

2. V calibration


- lsert test leads to COM & V position.

- Set the function switch to the V range.

1) Input 3V and press 3V button of SCAL350-IIt.

2) Input 30V and press 30V button of SCAL3504I.

3) Input 300V and press 300V button of SCAL350-IfI.

3. Temp calibration

- Insert RS-23X cable to DMM.

- Insert temp probe to Temp socket.

- Set the functon switch to the mV range.

1) Set a room temperature pressing with the arrows A & ‘I buttons of SCAL350-III.

2) input 15mV button of SCAL350-III.

3) Press yellow button of DMM and press “C button of SCAL-350III.

28

SCAL350-IV Calibration

I. Resistance calibration

- insert RS-232C cable to DMM.

- Insert Test leads to COM & SJ position.

- Set the function switch to the Ohm(Q) range.

1) input 1OOSJ and press 1OOQ button of SCAL350-IV.

2) Input 1kQ and press 1kQ button of SCAL350-IV.3) input 1 OkQ and press 1OkQ button of SCAL350-IV.

4) Input 100kB and press lOOk& button of SCAL350-IV.

5) Input IMQ and press 1MQ button of SCAL350-IV.

6) Input 9.85MQ and press 1OMQ button of SCAL350-IV.

2. Capacitance calibration

- Insert RS-232 cable to DMM.

- Insert a capacitor to Capacitance socket.- Set the function switch to the CAP range.

1) Input 46.5 ,uF and press 47pF button of SCAL350-IV.

2) Input 7OOnF and press 700nF button of SCAL350-IV.

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7-2. Software Calibration for 35OA Calibration Proccdurc

SC,4L360-I Calibration

1, D C V Caiibraiion

i ! Press ‘CAL ‘CNd’ b!l:t~~~. h4?&.; :;~rt? t<: scjund bccL\ t?: DIMM, If ~C)LI arc n o t a b l e t o h e a t

b e e p Sound, press ‘CAi- ON’ button agaIn.

2) Se: t h e f u n c t i o n swi?ch to the DCni V range.

31 I n p u t 200.0mV to CGM ant We. ana want untii drspiay IS s t a b i i i z e d .

4) Press ‘GK’ buttc:,n. ?;iat:c s;J~:;’ :c:: s~jrc; tc s(:ij;~d beep ai DMM, if you afe no? ab;e in

hear beep sound, press ‘OK’ button aiyavt.

5) Set t h e f u n c t i o n swich 10 the V rarlgc,

6) Input 2O.OOV to CGM and V/G. arid wait Until dsp~ay is sta.biilzt\d.

7) Press ‘OK’ button. Make sure to sound beep at DMM. if you are not able to hear beep

sound, press ‘OK’ button again.

8) Input 2O.OOV to CGM and V/Q, and wait until display IS stabi l ized.

9i Press ‘Gti’ button. Make sure to sound beep at DMM, if you are not able to ihear br=lep


101 Input 2OO.OV to CGM and V/Q, and wait untii display is stabilized.

11) Press ‘OK’ but;on. Make sure to sound b e e p a t D M M , if you are not able to h e a r

beep sound, press ‘OK’ button again.

12) Input 5OO.W to COM and V’Q. and wait until display is stabilized.

1 3 ) P r e s s ‘OK bgt!c;n M:_kc sm:: 10 sxm! b e e p a t D M M , i f ycti a r e rxt a b l e t o l?ear

beep sourld, press W:’ button agzin

141 Press -E N D C A L b~iio:; a-.!vj r-n&_! su:e 1:) srxjnd beep a.t D,UM.

2. ACV Callbratton

1) Press ‘CAL ON’ button. Make sure to sound beep at DMM, if you are not able to hear

beep sound, press ‘CAL ON’ button again.

21 Set the function switch to V, and press blue button to se? ACV.

3) Input 2V60Hz to COM and ‘\//.!‘J. wait tintil display is stabi l ized.

41 Press ‘OK’ buttcn. Make sutc ?c\ sourid beep sour~.I at DMM. if you are not a b l e to

hear beep sound, press ‘OK’ button again.

5) Press ‘END CAL’ butfGn and make sure to sound beep at DMM.

3. OHM Calibration


beep sound, press ‘CAL ON’ button again. -

2) Set the function switch to the OHM(Q) range.

3) input 200~2 to COM and V/Q, and wait until display is stabilized.

4) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able to hear beep

sound, press ‘OK’ button again.5) Input 2kSZ to COM and V/Q, and wait until display is stabilized.


sound, press ‘OK’ button.7) Input 20kQ to COM and V/Q, and wait until display is stabilized.


sound, press ‘OK’ button.

sound beep at DMM, if you are not able to hear

9) Input 200k.Q to COM and V/Q, wait until display is stabilized.

10) Press ‘OK’ button. Make sure to

beep sound, press ‘OK’ button.

11) Input 2MQ to COM and V/Q, and

12) Press ‘OK’ button. Make sure to


wait until display is stabilized.

sound beep at DMM, if you are not-able to hear

13) Input 20M/Q to COM and V/Q, and wait until display is stabilized.14) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able to hear


15) Press ‘END CAL’ button and make sure to sound beep at DMM.

4. CAPllND Calibration

1) Press “CAL ON’ button. Make sure to sound beep at DMM, if you are not able to hearbeep sound, press ‘CAL ON’button again.

2) Set the function switch to the CAP/L range.

3) Input 500.0nF to COM and CAP, and wait display is stabilized.



5) Input 5O.OuF to COM and CAP, and wait until display is stabilized.

6) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able-to hear beep

sound, press ‘OK’ button again.7) Press yellow button too set IND function.8) Input 10H to COM and L, wait until display is stabilized.

9) Press ‘OK’ button. Make to sound beep at DMM, if you are not able to hear beep


10) Press ‘END CAL’ and make sure to sound beep at DMM.

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5. Current Calibration

1) Press ‘CAL ON’ button. Make sure to sound beep at DMM, if you are nofable to hear


2) Set the function switch to the uA range.3) Adjust RI9 and set the display to +OCQl - 000.5.

4) Press ‘OFFSET’ button. Make sure to sound beep at DMM, if you are not able to hear

beep sound, press ‘OFFSET’ button again.

5) Input 2.0OOmA to COM and uA/mA, and wait until display is stbilized.6) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able to hear


7) Input 200uA to COM and uA/mA, and wait display is stabilized,

8) Press ‘GAIN’ button. Make sure to sound beep at DMM, if you are not able to hear

beep sound, press ‘GAIN’ button again.

9) Set the function switch to the mA range.

10) Input 200mA to COM and uA/mA, wait until display is stabilized.

11) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able to hear


12) Set the function switch to the A range.13) Input 1 OA to COM and A, wait until display is stabilized.

14) Press ‘OK’ button. Make sure to sound beep at DMM, if you are not able to hear



6. Temperature Calibration



2) Set the function switch to the A range and press Yellow button.

3) Set a room temperature pressing with arrows A and V buttons.

4) Press ‘TMP’ button. Make sure to sound beep at DMM, if you are not able to hear

beep sound, press ‘TMP’ button again.


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DIGITAL MWL TIMETER er - Conrad · l 4. A/D CONVERTER DESCRIPTION FEATURES q 40,000 Count...

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Transcript of DIGITAL MWL TIMETER er - Conrad · l 4. A/D CONVERTER DESCRIPTION FEATURES q 40,000 Count...