WHEATSTONE BRIDGE CIRCUIT DESIGN AND SIMULATION FOR TEMPERATURE SENSOR

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Group 01 <Please adapt this in the slide master>

MEASUREMENT AND SENSOR TECHNOLOGY

WHEATSTONE BRIDGE CIRCUIT DESIGN AND SIMULATION FOR

TEMPERATURE SENSOR

Group – 4A

PROJECT LAB EMBEDDED SYSTEMS

Chemnitz, 06/25/2015

CONTENTS

Introduction & Motivation

Objective

General Concept

Project Description

Conclusion

References

Seminar Automotive SensorsUniv.-Prof. Dr.-Ing. O. KanounChair for Measurement and Sensor Technology

INTRODUCTION & MOTIVATIONTemperature plays an important role in many industries both

electrical & non-electrical for analyzing properties and behavior of

various objects.

Industrial Instrumentations.

Hot Wire Anemometers.

Lab Quality Measurements.


INTRODUCTION & MOTIVATIONAir, Gas & Liquid Monitoring.

Petrochemicals.

Air Conditioning & Refrigeration.

Textile Production

Plastics Processing

Remote temperature Sensing

for Automation Systems.


OBJECTIVE

To Design a Bridge circuit to simulate temperature sensor.

To Simulate in LTSpice, Labview & Matlab to analyze the behavior

of the temperature sensor.

To design a PCB considering all the given design rules.


GENERAL CONCEPT – TEMPERATURE SENSOR


Feature Thermistor RTD Thermocouples

Temperature Range (in °C) -90 to 130 -200 to 850 -185 to 2300

Material Used Ceramic or polymer Pure Metals Alloys

Accuracy/Linearity Poor Highly Accurate Fairly Good

Sensitivity Several Ω /°C 0.00385 Ω /°C (for Platinum)

Tens of Micro-volts per degree

Figure

BLOCK DIAGRAM


Resistance Change

RTD Wheatstone Bridge

Difference Amplifier

Voltage Change

Temperature Change

Voltage Response

RESISTANCE TEMPERATURE DETECTOR

Available in 2-wire, 3-wire & 4-wire configuration.

Variety of packages - wire-round and thin-film

Excellent stability and reproducibility

Very good Linearity

Extremely accurate



RT = Resistance of the wire at temperature T°CRo = Resistance of the wire at temperature 0°CT = Temperature in °Cα = Temperature co-efficient of resistance (°C-1)

For Platinum wire RTD




Relation between temperature and resistance:

RT = R0[1 + AT + BT2 + CT3(T – 100)] (-200°C < T < 0°C)

RT = R0[1 + AT + BT2] (0°C < T < 850°C)

Where RT = Resistance of the wire at temperature T°C

Ro = Resistance of the wire at temperature 0°C

α = 0.00385 (°C-1)

A = 3.9083 X 10 -3°C-1

B = -5.775 X 10 -7°C-1

C = -4.183 X 10-12°C-1

WHEATSTONE BRIDGE


DIFFERENTIAL AMPLIFIER


CIRCUIT DIAGRAM


Wheatstone Bridge Buffer Difference

Amplifier

Voltage Response

Temperature Change

LTSPICE SIMULATION RESULT


Temperature (°C)

Out

put V

olta

ge

(vol

ts)

LABVIEW SIMULATION BLOCK DIAGRAM


LabVIEW Block Diagram

LABVIEW SIMULATION RESULT


LabVIEW front panel

MATLAB SIMULATION RESULTS


PCB DESIGN

Single Sided PCB PCB Size – 0.96 X 1.91 inch Space Between copper layers – 0.2mm Smallest Track Width – 0.2mm Layer thickness – 35µm


CONCLUSION

Bridge circuit was designed to simulate the temperature sensor.

Simulation completed in LTSpice, Labview and Matlab.

The voltage output was verified.

PCB was designed adhering to rules and guidelines.


REFERENCES Ramon Pallas-Areny, John G. Webster. “Sensors and signal

conditioning” – 2nd ed. A Wiley – Interscience Publication. H S Kalsi, “Electronic Instrumentation” Tata McGraw-Hill, 2009 D.Patranabis, “Sensors and Transducers” – 2nd ed. PHI Learning

Pvt. Ltd., 2003. A.K. Shawney, Puneet Sawhney, “A Course in Electrical and

Electronic Measurements and Instrumentation” – Dhanpat Rai Publications, 2012.

Bela G. Liptak, “Instrument Engineers’ Handbook: Process Measurement and Analysis” – 3rd ed., CRC Press, 1995.

Doeblin, “Measurement Systems Applications and Design” – 4th ed., Mcgraw-Hill College, 1989.



ADDITIONAL INFORMATIONTHEORETICAL CALCULATIONS

Temperature

(°C)

Resistance

(Ω)

Voltage

(volts)

Amplifier

Gain

Output Voltage

(Volts)

-200 18.52 -3.437394533 2.2 -7.56227

-150 39.72 -2.157171486 2.2 -4.74578

-100 60.26 -1.239860227 2.2 -2.72769

-50 80.31 -0.546004104 2.2 -1.20121

0 100 0 2.2 0

50 119.4 0.442114859 2.2 0.972653

100 138.51 0.807303677 2.2 1.776068

150 157.33 1.1139393 2.2 2.450666

200 175.86 1.374972812 2.2 3.02494

250 194.1 1.599795988 2.2 3.519551

300 212.05 1.795385355 2.2 3.949848


ADDITIONAL INFORMATIONTHEORETICAL CALCULATIONS

Temperature

(°C)

Resistance

(Ω)

Voltage

(volts)

Amplifier

Gain

Output Voltage

(Volts)

350 229.72 1.96712362 2.2 4.327672

400 247.09 2.118902878 2.2 4.661586

450 264.18 2.254105113 2.2 4.959031

500 280.98 2.375190299 2.2 5.225419

550 297.49 2.484213439 2.2 5.46527

600 313.71 2.582847889 2.2 5.682265

650 329.64 2.672469975 2.2 5.879434

700 345.28 2.754222063 2.2 6.059289

750 360.64 2.829107329 2.2 6.224036

800 375.7 2.89783477 2.2 6.375236

850 390.48 2.961180884 2.2 6.514598

WHEATSTONE BRIDGE CIRCUIT DESIGN AND SIMULATION FOR TEMPERATURE SENSOR

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