Choosing the Right Sensors for Industrial Applications

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Q&A at the end of the presentation

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Before We Start

Moderator

Randy Frank Design World

Presenters

Emmy Denton Texas Instruments

Tim Shotter All Sensors

Dan Bruski SICK

in

Industrial Environments

Emmy Denton

Applications Engineer

May 29, 2013

Temperature Sensor Applications

Temperature Sensors have

3 key functions in electronic

systems

• Calibration

• Monitoring & Protection

• Control

Temp sensing is

EVERYWHERE!

– Industrial: Factory Automation,

Medical, Down Hole Drilling,

Instrumentation …

6

Common Temperature Sensing Technologies

Criteria

ATS

Thermistor Thermocouple

RTD

Temp Range (°C) -55 to +150 (-55 to +200 digital)

-100 to +500 (-60 to +200 SMD)

-267 to +2316 -240 to 700

Accuracy Good Good Good Best

Linearity Best Least Better Better

Sensitivity Better Best Least Less

Circuit Simplicity Simplest Simpler Complex Complex

Power Consumption Lowest Low High High

Cost $ $ $$ $$$

7

Local Digital

Reports temperature at location of the

sensor

Small

Low Power

Popular Interfaces (I2C, SPI, One-wire …)

Highest Temp (200°C)

Highest Accuracy (0.5°C)

Ind. Standard (LM75)

Remote Digital

Measure any Diode, Transistor, or

CPU/GPU/FPGA

Multiple Channels

Int. Power Monitor

Beta Correction

Contactless IR

Measures passive IR to determine

object temperature without making

contact

Switches/Thermostat

Simple hardware over temperature

protection

Dual Alerts

Resistor Prog

Pin Programmable

Factory Preset

Analog Temperature Outputs

Fan Control /HW Monitors

Complex with Many Functions in

addition to temperature sensing

2 Wire Interface

Fan Control Monitor

Monitor & Control (ADC and DAC)

Voltage Comparators

Integrated Circuit Thermal Management Solutions

Local Analog

Voltage output proportional to

temperature

Smallest

Highest Accuracy

Lowest Power

Highest Temp

Most Popular

Low Cost

8

Downhole Drilling Tools

LM95172

• Located at the tip of the drill in order to

protect the other circuitry above

Reasons for Temp Sensing

• Over-Temp Protection of PCB Components

• Predict life expectancy of tool

• Customer billing purposes

• Tool Oil Degradation

Key Specifications

• Up to +200°C temperature range

• Digital Interface – redundant ADC

• High accuracy and resolution

• Alarm output and shutdown mode

• Requires reliability – additional qualification required

• Packaging must withstand extensive temperature

(usually ceramic or die)

Temp Range

(°C)

Accuracy (°C)

+130 to +160 ±1.0

+160 to +175 ±2.0

+175 to 200 ±3.0

+120 to +130 ±2.0

-40 to +120 ±3.5

9

Thermocouple Cold Junction Compensation

Reasons for Temp Sensing • Thermocouple measures difference temperature of two

junctions

– Junction at zone being measured

– Junction back to copper

• Required to determine temperature of zone being

measured

Key specifications

• Up to +70°C - 85°C temperature range

• ADC is usually available in AFE

• Accuracy added to accuracy of zone being measured

• Must be mounted on isothermal block for good temperature

conduction

T_cold

T_hot

10

Analog Temperature Sensing Options

• Most Micros Include Multiple Channel ADCs

• Analog Temp Sensor Advantages:

Higher accuracy over wider temperature range

Linear across temp range

Lower Power Dissipation – draw less than 10uA over temp range

Simpler design that utilizes less board space – no additional external components

Simpler to use

LMT84 Curve

11

ATS

THERMISTOR

Output Voltage vs. Temperature (°C)

ATS

THERMISTOR

vs.

ATS

12

Analog Temp Sensor Accuracy

• Accuracy is very linear for 96

units plotted

• ±0.7°C Max and Min Accuracy

over 0 to 150°C

• Sensing temps approaching

200°C possible

• Some Devices Can Achieve +/-

0.1°C Spread without

Temperature Calibration!

13

THANK YOU!

– Emmy Denton

All Sensors

PRESSURE SENSORS…

RESOLUTION AND BANDWIDTH

Typical Applications

All Sensors

Familiar Specifications • Pressure Range

• Sensitivity

• Offset

• Linearity

• Temperature Effects

• Accuracy

All Sensors

Compensation Techniques

All Sensors

Familiar Trade-offs

All Sensors

What Your Mom Didn’t Tell You…

All Sensors

System Basics Review

All Sensors

Application BW/Resolution

All Sensors

All Sensors

BW/Resolution Isolines

All Sensors

Possible Compensation

Revised BW/Resolution Trade-offs

All Sensors

• To know the location of something

• To move a target with respect to that known location

• Everything’s relative o Objects are positioned with respect to something fixed

o Key for evaluating specs like accuracy, repeatability, resolution

Focus application areas

• Positioning in manufacturing Knives, slitters, saws, welding tips, drills, tools

• Logistics Cranes, ASRS, shuttles, rail cars

What is “positioning?” What are we positioning?

Rotary and wire draw encoders

Linear magnetic encoders

Lasers Hybrid

Positioning Technology Choices

High speed

High resolution

Low cost

Slippage and wear

errors

Mechanical

High speed

High resolution

Rugged in challenging

environments

Difficulty with non-linear paths

Strict mounting requirements

Cost

Navigates non-linear paths

Path can be obstructed by other

vehicles or objects

Need to mount reference tape

Simple setup

Non-contact – long life

Many choices of range, precision,

outputs

Line of sight only

Optically challenging environments

Range

•Sensor must not only be able to measure the absolute distance from the sensor to the target to be positioned, but also have the appropriate span.

Resolution

•How small of a movement is need to be controlled?

Repeatability

•Repeatability is KEY. This describes how close to the desired location it will be when the sensor output indicates it has reached its final position

Output rate

•The output rate of the sensor is how often the sensor updates the measured position and needs to be matched up with the speed of the target.

Output type

•The output type simply needs to match the input of the control system/PLC/PC.

Selection Criteria

• A reflective target is preferred over natural targets for positioning o Strong and consistent signal return

o “Safe” – if reflector is blocked, an erroneous position is not returned

• Response time vs. output rate o Response time refers to lateral movement into the beam – used for detection, not positioning

o Output rate is what matters after the target is locked-in

• Accuracy trap o Don’t get hung up on an accuracy spec, because you don’t need it for positioning applications

until you replace a sensor

• Excess gain o Don’t worry about using a sensor with way more range than needed – this gives you useful

excess gain

• Long range alignment o Utilize vendor-supplied alignment brackets

Tips and Tricks

30

Questions?

Design World Randy Frank R.Frank@ieee.org Twitter: @SensorTips

All Sensors Tim Shotter TShotter@allsensors.com Phone: 408.225.4314 Twitter: @AllSensors

SICK Dan Bruski Dan.Bruski@sick.com Phone: 612.217.1326

Texas Instruments Emmy Denton emmy.smaragda.denton@ti.com Phone: 408.721.3267

Thank You

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