Sensors and Transducers Second Edition D. Patranabis
Sensors and Transducers Second Edition ion D. PATRANABIS Professor Department of Instrumentation and Electronics Engineering Jadavpur University Salt Lake Campus Kolkata Delhi-110092 2013
SENSORS AND TRANSDUCERS, Second Edition D. Patranabis 2003 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN-978-81-203-2198-4 The export rights of this book are vested solely with the publisher. Twelfth Printing (Second Edition) January, 2013 Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi-110092 and Printed by Perfect Impression, New Delhi-110016.
Dedicated to My Parents
Contents Preface xi Chapter 1 GETTING STARTED! 1 13 1.1 What are Sensors/Transducers? 1 1.2 Principles 1 1.3 Classification 3 1.4 Parameters 5 1.4.1 Characteristics 5 Static characteristics 5 Dynamic characteristics 9 1.5 Environmental Parameters (EP) 9 1.6 Characterization 10 Electrical characterization 10 Mechanical and thermal characterization 11 Optical characterization 13 Chemical/biological characterization 13 Review Questions 13 Chapter 2 MECHANICAL AND ELECTROMECHANICAL SENSORS 14 67 2.1 Introduction 14 2.2 Resistive Potentiometer 15 2.3 Strain Gauge 18 2.3.1 Resistance Strain Gauge 19 2.3.2 Semiconductor Strain Gauges 25 2.4 Inductive Sensors 29 2.4.1 Sensitivity and Linearity of the Sensor 34 2.4.2 Ferromagnetic Plunger Type Transducers 36 2.4.3 Inductance with a Short-circuited Sleeve 39 2.4.4 The Transformer Type Transducer 41 2.4.5 Electromagnetic Transducer 43 2.4.6 Magnetostrictive Transducer 45 2.4.7 Materials Some Comments 47 2.5 Capacitive Sensors 47 2.5.1 The Parallel Plate Capacitive Sensor 49 2.5.2 Serrated Plate Capacitive Sensor 50 2.5.3 Variable Permittivity or Variable Thickness Dielectric Capacitive Sensor 51 v
vi Contents 2.5.4 Stretched Diaphragm Variable Capacitance Transducer 52 2.5.5 Electrostatic Transducer 54 2.5.6 Piezoelectric Elements 55 Piezoelectric materials 56 Deformation modes and multimorphs 61 2.5.7 The PZT Family 62 2.6 Force/Stress Sensors Using Quartz Resonators 63 2.7 Ultrasonic Sensors 64 Review Questions 65 Chapter 3 THERMAL SENSORS 68 135 3.1 Introduction 68 3.2 Gas Thermometric Sensors 69 3.3 Thermal Expansion Type Thermometric Sensors 72 3.4 Acoustic Temperature Sensor 74 3.5 Dielectric Constant and Refractive Index Thermosensors 77 3.6 Helium Low Temperature Thermometer 78 3.7 Nuclear Thermometer 78 3.8 Magnetic Thermometer 79 3.9 Resistance Change Type Thermometric Sensors 80 3.9.1 Metal Resistance Thermometric Sensors 83 3.9.2 Thermistors 88 3.10 Thermoemf Sensors 91 3.10.1 Materials for Thermoemf Sensors 96 3.10.2 E T Relations 99 3.10.3 Thermocouple Construction 100 3.10.4 Reference Temperature 101 3.10.5 Thermosensors Using Semiconductor Devices 102 3.11 Junction Semiconductor Types 103 3.11.1 The PTAT Sensor 105 3.12 Thermal Radiation Sensors 108 3.12.1 Detectors 115 3.12.2 Pyroelectric Thermal Sensors 120 3.13 Quartz Crystal Thermoelectric Sensors 123 3.14 NQR Thermometry 125 3.15 Spectroscopic Thermometry 126 3.16 Noise Thermometry 128 3.17 Heat Flux Sensors 130 Review Questions 133 Chapter 4 MAGNETIC SENSORS 136 182 4.1 Introduction 136 4.2 Sensors and the Principles Behind 137 4.2.1 The Yoke Coil Sensors 142 4.2.2 The Coaxial Type Sensors 145 4.2.3 Force and Displacement Sensors 146
Contents vii 4.3 Magnetoresistive Sensors 148 4.3.1 Anisotropic Magnetoresistive Sensing 148 4.3.2 Semiconductor Magnetoresistors 152 Effect of geometry 153 Effect of material 154 4.3.3 Active Semiconductor Magnetic Sensors 156 4.4 Hall Effect and Sensors 156 4.4.1 The Hall Effect 157 4.4.2 The Hall Effect Sensor 159 Sensor geometry and fabrication 160 Sensor performance 162 4.5 Inductance and Eddy Current Sensors 164 4.5.1 Variable Inductance Sensors 164 4.5.2 The Plunger Type Sensors 165 4.5.3 Variable Gap Sensors 167 4.5.4 Linear Variable Differential Transformer (LVDT) 168 4.6 Angular/Rotary Movement Transducers 171 4.6.1 Synchros 171 4.6.2 Synchro-resolvers 174 4.7 Eddy Current Sensors 175 4.8 Electromagnetic Flowmeter 177 4.9 Switching Magnetic Sensors 178 4.9.1 The Wiegand Sensor 179 4.9.2 The Pulse Wire Sensor 180 4.10 SQUID Sensors 180 Review Questions 181 Chapter 5 RADIATION SENSORS 183 233 5.1 Introduction 183 5.2 Basic Characteristics 184 5.3 Types of Photosensistors/Photodetectors 190 5.3.1 The Photoemissive Cell and the Photomultiplier 190 5.3.2 The Photoconductive Cell 195 The LDR 195 Photocurrent 198 Noise 201 5.3.3 Photovoltaic and Photojunction Cells 204 Reverse biased junction photocell 208 5.3.4 Position-sensitive Cell 213 5.3.5 Photoresistors and PhotoFETs and Other Devices 214 5.4 X-ray and Nuclear Radiation Sensors 216 5.4.1 The Ionization Chamber 218 5.4.2 Proportional Counters 220 5.4.3 Geiger Counters 221 5.4.4 Scintillation Detectors 222
viii Contents 5.4.5 Solid State Detectors 224 5.4.6 Plastic Film and Luminescent Detectors 226 5.4.7 Factors Affecting Radiation Measurement 226 5.5 Fibre Optic Sensors 227 5.5.1 Temperature Sensors 228 5.5.2 Liquid Level Sensing 229 5.5.3 Fluid Flow Sensing 230 5.5.4 Microbend Sensors 230 Review Questions 231 Chapter 6 ELECTROANALYTICAL SENSORS 234 261 6.1 Introduction 234 6.2 The Electrochemical Cell 234 6.3 The Cell Potential 236 6.4 Standard Hydrogen Electrode (SHE) 237 6.5 Liquid Junction and Other Potentials 238 6.6 Polarization 239 Concentration polarization 239 Reaction polarization 240 Adsorption/desorption/crystallization polarization 240 Charge transfer polarization 240 6.7 Reference Electrodes 240 6.8 Sensor Electrodes 242 6.8.1 Metal Electrodes 242 6.8.2 Membrane Electrodes 244 The ion selective membrane electrodes 244 Molecular selective electrodes 250 6.8.3 Temperature Sensing Electrodes 253 6.9 Electroceramics in Gas Media 254 6.9.1 Ionic Conductors 255 Zirconia 255 NASICON 257 b-alumina 257 Tin oxide 257 Zinc oxide 258 Titania (TiO 2 ) 258 Pervoskites 259 Varistors 259 6.10 ChemFET 259 Review Questions 260 Chapter 7 SMART SENSORS 262 281 7.1 Introduction 262 7.2 Primary Sensors 264 7.3 Excitation 267
Contents ix 7.4 Amplification 267 7.5 Filters 267 7.6 Converters 267 7.7 Compensation 269 7.7.1 Nonlinearity 269 Approximation and regression 272 7.7.2 Noise and Interference 274 7.7.3 Response Time 275 7.7.4 Drift 275 7.7.5 Cross-sensitivity 276 7.8 Information Coding/Processing 277 7.9 Data Communication 278 7.9.1 Standards for Smart Sensor Interface 279 7.10 The Automation 280 Review Questions 281 Chapter 8 RECENT TRENDS IN SENSOR TECHNOLOGIES 282 299 8.1 Introduction 282 8.2 Film Sensors 282 8.2.1 Thick Film Sensors 283 8.2.2 Thin Film Sensors 284 8.3 Semiconductor IC Technology Standard Methods 287 8.4 Microelectromechanical Systems (MEMS) 292 8.4.1 Micromachining 292 8.4.2 Some Application Examples 294 8.5 Nano-sensors 296 Review Questions 298 Chapter 9 SENSORS THEIR APPLICATIONS 300 325 9.1 Introduction 300 9.2 On-board Automobile Sensors (Automotive Sensors) 300 9.2.1 Flow-rate Sensors 300 9.2.2 Pressure Sensors 301 9.2.3 Temperature Sensors 302 9.2.4 Oxygen Sensors 303 9.2.5 Torque and Position Sensors 305 9.3 Home Appliance Sensors 306 9.4 Aerospace Sensors 310 9.4.1 Static Pressure Sensors 310 9.4.2 Temperature Sensing 311 9.4.3 Fluid Velocity Sensors 312 9.4.4 Sensing Direction of Air-flow 313 9.4.5 Measuring Air-speed on Aircrafts 313 9.4.6 Monitoring Strain, Force, Thrust, and Acceleration 314
x Contents 9.5 Sensors for Manufacturing 314 9.5.1 Sensors 315 Distance sensing 316 9.6 Medical Diagnostic Sensors 319 9.6.1 Sensors 319 Radiation 319 Biomechanics 320 Temperature 320 Electromagnetic variable 320 Chemical and electrochemical sensors 320 Variables related to blood flow 321 Kinematic and geometric 321 9.7 Sensors for Environmental Monitoring 321 9.7.1 Pollution Hazards 322 9.7.2 Sensing Environmental Pollution 323 9.7.3 Ecological Studies of Air 323 Review Questions 324 Bibliography 327 330 Index 331 335
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