Sensor technology handbook (2005)

Sensor Technology Handbook

This page intentionally left blank

Sensor Technology Handbook

Editor-in-Chief

Jon S. Wilson

AMSTERDAM • BOSTON • HEIDELBERG • LONDON

NEW YORK • OXFORD • PARIS • SAN DIEGO

SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO

Newnes is an imprint of Elsevier

Newnes is an imprint of Elsevier

30 Corporate Drive, Suite 400, Burlington, MA 01803, USA

Linacre House, Jordan Hill, Oxford OX2 8DP, UK

Copyright © 2005, Elsevier Inc. All rights reserved.

No part of this publication may be reproduced, stored in a retrieval

system, or transmitted in any form or by any means, electronic,

mechanical, photocopying, recording, or otherwise, without the prior

written permission of the publisher.

Permissions may be sought directly from Elsevier’s Science & Technology

Rights Department in Oxford, UK: phone: (+44) 1865 843830, fax: (+44)

1865 853333, e-mail: [email protected]. You may also com￾plete your request on-line via the Elsevier homepage (http://elsevier.com),

by selecting “Customer Support” and then “Obtaining Permissions.”

Recognizing the importance of preserving what has been written,

Elsevier prints its books on acid-free paper whenever possible.

Library of Congress Cataloging-in-Publication Data

(Application submitted.)

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library.

ISBN: 0-7506-7729-5

For information on all Newnes publications visit our Web site at:

www.books.elsevier.com

04 05 06 07 08 09 10 9 8 7 6 5 4 3 2 1

Printed in the United States of America

Preface .......................................................................................................................ix

CHAPTER 1: Sensor Fundamentals ............................................................................1

1.1 Basic Sensor Technology ................................................................................................ 1

1.2 Sensor Systems ............................................................................................................ 15

CHAPTER 2: Application Considerations ................................................................21

2.1 Sensor Characteristics .................................................................................................. 22

2.2 System Characteristics ................................................................................................. 22

2.3 Instrument Selection .................................................................................................... 23

2.4 Data Acquisition and Readout ..................................................................................... 26

2.5 Installation .................................................................................................................. 26

CHAPTER 3: Measurement Issues and Criteria .......................................................29

CHAPTER 4: Sensor Signal Conditioning ................................................................31

4.1 Conditioning Bridge Circuits ....................................................................................... 31

4.2 Amplifiers for Signal Conditioning ............................................................................... 45

4.3 Analog to Digital Converters for Signal Conditioning ................................................... 92

4.4 Signal Conditioning High Impedance Sensors ........................................................... 108

CHAPTER 5: Acceleration, Shock and Vibration Sensors .....................................137

5.1 Introduction .............................................................................................................. 137

5.2 Technology Fundamentals ........................................................................................ 137

5.3 Selecting and Specifying Accelerometers ................................................................... 150

5.4 Applicable Standards ............................................................................................... 153

5.5 Interfacing and Designs ............................................................................................. 155

CHAPTER 6: Biosensors ..........................................................................................161

6.1 Overview: What Is a Biosensor? ................................................................................. 161

6.2 Applications of Biosensors ......................................................................................... 164

6.3 Origin of Biosensors .................................................................................................. 168

6.4 Bioreceptor Molecules ............................................................................................... 169

6.5 Transduction Mechanisms in Biosensors ..................................................................... 171

6.6 Application Range of Biosensors ................................................................................ 173

6.7 Future Prospects ........................................................................................................ 177

v

Contents

vi

Contents

CHAPTER 7: Chemical Sensors ...............................................................................181

7.1 Technology Fundamentals ......................................................................................... 181

7.2 Applications .............................................................................................................. 188

CHAPTER 8: Capacitive and Inductive Displacement Sensors .............................193

8.1 Introduction .............................................................................................................. 193

8.2 Capacitive Sensors ..................................................................................................... 194

8.3 Inductive Sensors ....................................................................................................... 196

8.4 Capacitive and Inductive Sensor Types ....................................................................... 198

8.5 Selecting and Specifying Capacitive and Inductive Sensors ......................................... 200

8.6 Comparing Capacitive and Inductive Sensors ............................................................. 203

8.7 Applications .............................................................................................................. 204

8.8 Latest Developments ................................................................................................. 221

8.9 Conclusion ................................................................................................................ 222

CHAPTER 9: Electromagnetism in Sensing ...........................................................223

9.1 Introduction .............................................................................................................. 223

9.2 Electromagnetism and Inductance ............................................................................. 223

9.3 Sensor Applications ................................................................................................... 226

9.4 Magnetic Field Sensors .............................................................................................. 232

9.5 Summary ................................................................................................................... 235

CHAPTER 10: Flow and Level Sensors ...................................................................237

10.1 Methods for Measuring Flow ................................................................................... 237

10.2 Selecting Flow Sensors ............................................................................................ 246

10.3 Installation and Maintenance ................................................................................... 247

10.4 Recent Advances in Flow Sensors ............................................................................ 249

10.5 Level Sensors ........................................................................................................... 250

10.6 Applicable Standards ............................................................................................... 254

CHAPTER 11: Force, Load and Weight Sensors ....................................................255

11.1 Introduction ............................................................................................................ 255

11.2 Quartz Sensors ........................................................................................................ 255

11.3 Strain Gage Sensors ................................................................................................ 262

CHAPTER 12: Humidity Sensors ............................................................................271

12.1 Humidity ................................................................................................................. 271

12.2 Sensor Types and Technologies ................................................................................ 271

12.3 Selecting and Specifying Humidity Sensors .............................................................. 275

12.4 Applicable Standards ............................................................................................... 279

12.5 Interfacing and Design Information ......................................................................... 280

CHAPTER 13: Machinery Vibration Monitoring Sensors .....................................285

13.1 Introduction ............................................................................................................ 285

13.2 Technology Fundamentals ....................................................................................... 288

13.3 Accelerometer Types ................................................................................................ 291

13.4 Selecting Industrial Accelerometers .......................................................................... 294

13.5 Applicable Standards ............................................................................................... 303

vii

Contents

13.6 Latest and Future Developments .............................................................................. 304

13.7 Sensor Manufacturers .............................................................................................. 304

13.8 References and Resources ........................................................................................ 305

CHAPTER 14: Optical and Radiation Sensors .......................................................307

14.1 Photosensors ........................................................................................................... 307

14.2 Thermal Infrared Detectors ...................................................................................... 317

CHAPTER 15: Position and Motion Sensors ..........................................................321

15.1 Contact and Non-contact Position Sensors .............................................................. 321

15.2 String Potentiometer and String Encoder Engineering Guide .................................... 370

15.3 Linear and Rotary Position and Motion Sensors ........................................................ 379

15.4 Selecting Position and Displacement Transducers ..................................................... 401

CHAPTER 16: Pressure Sensors ..............................................................................411

16.1 Piezoresistive Pressure Sensing ................................................................................. 411

16.2 Piezoelectric Pressure Sensors ....................................................................433

CHAPTER 17: Sensors for Mechanical Shock ........................................................457

17.1 Technology Fundamentals ....................................................................................... 457

17.2 Sensor Types, Advantages and Disadvantages .......................................................... 459

17.3 Selecting and Specifying .......................................................................................... 461

17.4 Applicable Standards ............................................................................................... 473

17.5 Interfacing Information ............................................................................................ 474

17.6 Design Techniques and Tips, with Examples ............................................................. 478

17.7 Latest and Future Developments .............................................................................. 480

CHAPTER 18: Test and Measurement Microphones ............................................481

18.1 Measurement Microphone Characteristics ............................................................... 481

18.3 Traditional Condenser Microphone Design ............................................................... 483

18.4 Prepolarized (or Electret) Microphone Design ........................................................... 484

18.5 Frequency Response ................................................................................................ 484

18.6 Limitations on Measurement Range ......................................................................... 490

18.7 Effect of Environmental Conditions .......................................................................... 491

18.8 Microphone Standards ............................................................................................ 492

18.9 Specialized Microphone Types .................................................................................. 494

18.10 Calibration ............................................................................................................ 497

18.11 Major Manufacturers of Test and Measurement Microphones ................................ 499

CHAPTER 19: Strain Gages .....................................................................................501

19.1 Introduction to Strain Gages .................................................................................... 501

19.2 Strain-Gage Based Measurements ........................................................................... 511

19.3 Strain Gage Sensor Installations ............................................................................... 522

CHAPTER 20: Temperature Sensors ......................................................................531

20.1 Sensor Types and Technologies ................................................................................ 531

20.2 Selecting and Specifying Temperature Sensors ......................................................... 535

viii

CHAPTER 21: Nanotechnology-Enabled Sensors .................................................563

21.1 Possibilities .............................................................................................................. 564

21.2 Realities ................................................................................................................... 566

21.3 Applications ............................................................................................................ 567

23.4 Summary ................................................................................................................. 571

CHAPTER 22: Wireless Sensor Networks: Principles and Applications ...............575

22.1 Introduction to Wireless Sensor Networks ................................................................ 575

22.2 Individual Wireless Sensor Node Architecture ........................................................... 576

22.3 Wireless Sensor Networks Architecture .................................................................... 577

22.4 Radio Options for the Physical Layer inWireless Sensor Networks ............................. 580

22.5 Power Consideration in Wireless Sensor Networks ................................................... 583

22.6 Applications of Wireless Sensor Networks ....................................................... 585

22.7 Future Developments ............................................................................................... 588

APPENDIX A: Lifetime Cost of Sensor Ownership ...............................................591

APPENDIX B: Smart Sensors and TEDS FAQ .........................................................597

APPENDIX C: Units and Conversions ....................................................................601

APPENDIX D: Physical Constants ...........................................................................607

APPENDIX E: Dielectric Constants .........................................................................615

APPENDIX F: Index of Refraction ..........................................................................617

APPENDIX G: Engineering Material Properties ....................................................619

APPENDIX H: Emissions Resistivity .......................................................................625

APPENDIX I: Physical Properties of Some Typical Liquids ...................................629

APPENDIX J: Speed of Sound in Various Bulk Media ..........................................631

APPENDIX K: Batteries ...........................................................................................633

APPENDIX L: Temperatures ...................................................................................635

Contributor’s Biographies .....................................................................................637

Contributing Companies .......................................................................................647

Sensor Suppliers .....................................................................................................655

Subject Index ..........................................................................................................683

Sensor Technology Index ......................................................................................690

Contents

ix

Preface

The first decade of the 21st century has been labeled by some as the “Sensor Decade.”

With a dramatic increase in sensor R&D and applications over the past 15 years, sen￾sors are certainly poised on the brink of a revolution similar to that experienced in

microcomputers in the 1980s. Just in automobiles alone, sensing needs are growing

by leaps and bounds, and the sensing technologies used are as varied as the applica￾tions. Tremendous advances have been made in sensor technology and many more are

on the horizon.

In this volume, we attempted to balance breadth and depth in a single, practical and

up-to-date resource. Understanding sensor design and operation typically requires a

cross-disciplinary background, as it draws from electrical engineering, mechanical

engineering, physics, chemistry, biology, etc. This reference pulls together the most

crucial information needed by those who design sensor systems and work with sen￾sors of all types, written by experts from industry and academia. While it would be

impossible to cover each and every sensor in use today, we attempted to provide as

broad a range of sensor types and applications as possible. The latest technologies,

from piezo materials to micro and nano sensors to wireless networks, are discussed,

as well as the tried and true methodologies. In addition, information on design, inter￾facing and signal conditioning is given for each sensor type.

Organized primarily by sensor application, the book is cross-referenced with indices

of sensor technology. Manufacturers are listed by sensor type. The other contributors

and I have attempted to provide a useful handbook with technical explanations that

are clear, simple and thorough. We will also attempt to keep it updated as the technol￾ogy advances.

Jon S. Wilson

Chandler, Arizona

October, 2004

This page intentionally left blank

1

C H A P T E R 1

Sensor Fundamentals

1.1 Basic Sensor Technology

Dr. Tom Kenny, Department of Mechanical Engineering,

Stanford University

A sensor is a device that converts a physical phenomenon into an electrical signal. As

such, sensors represent part of the interface between the physical world and the world

of electrical devices, such as computers. The other part of this interface is represented

by actuators, which convert electrical signals into physical phenomena.

Why do we care so much about this interface? In recent years, enormous capability

for information processing has been developed within the electronics industry. The

most significant example of this capability is the personal computer. In addition, the

availability of inexpensive microprocessors is having a tremendous impact on the

design of embedded computing products ranging from automobiles to microwave

ovens to toys. In recent years, versions of these products that use microprocessors for

control of functionality are becoming widely available. In automobiles, such capabil￾ity is necessary to achieve compliance with pollution restrictions. In other cases, such

capability simply offers an inexpensive performance advantage.

All of these microprocessors need electrical input voltages in order to receive instruc￾tions and information. So, along with the availability of inexpensive microprocessors

has grown an opportunity for the use of sensors in a wide variety of products. In

addition, since the output of the sensor is an electrical signal, sensors tend to be char￾acterized in the same way as electronic devices. The data sheets for many sensors are

formatted just like electronic product data sheets.

However, there are many formats in existence, and there is nothing close to an in￾ternational standard for sensor specifications. The system designer will encounter a

variety of interpretations of sensor performance parameters, and it can be confusing.

It is important to realize that this confusion is not due to an inability to explain the

meaning of the terms—rather it is a result of the fact that different parts of the sensor

community have grown comfortable using these terms differently.

Chapter 1

2

Sensor Data Sheets

It is important to understand the function of the data sheet in order to deal with this

variability. The data sheet is primarily a marketing document. It is typically designed

to highlight the positive attributes of a particular sensor and emphasize some of the

potential uses of the sensor, and might neglect to comment on some of the negative

characteristics of the sensor. In many cases, the sensor has been designed to meet a

particular performance specification for a specific customer, and the data sheet will

concentrate on the performance parameters of greatest interest to this customer. In

this case, the vendor and customer might have grown accustomed to unusual defini￾tions for certain sensor performance parameters. Potential new users of such a sensor

must recognize this situation and interpret things reasonably. Odd definitions may be

encountered here and there, and most sensor data sheets are missing some pieces of

information that are of interest to particular applications.

Sensor Performance Characteristics Definitions

The following are some of the more important sensor characteristics:

Transfer Function

The transfer function shows the functional relationship between physical input

signal and electrical output signal. Usually, this relationship is represented as

a graph showing the relationship between the input and output signal, and the

details of this relationship may constitute a complete description of the sen￾sor characteristics. For expensive sensors that are individually calibrated, this

might take the form of the certified calibration curve.

Sensitivity

The sensitivity is defined in terms of the relationship between input physical

signal and output electrical signal. It is generally the ratio between a small

change in electrical signal to a small change in physical signal. As such, it

may be expressed as the derivative of the transfer function with respect to

physical signal. Typical units are volts/kelvin, millivolts/kilopascal, etc.. A

thermometer would have “high sensitivity” if a small temperature change

resulted in a large voltage change.

Span or Dynamic Range

The range of input physical signals that may be converted to electrical sig￾nals by the sensor is the dynamic range or span. Signals outside of this range

are expected to cause unacceptably large inaccuracy. This span or dynamic

range is usually specified by the sensor supplier as the range over which other

performance characteristics described in the data sheets are expected to apply.

Typical units are kelvin, pascal, newtons, etc.

Sensor Fundamentals

3

Accuracy or Uncertainty

Uncertainty is generally defined as the largest expected error between actual

and ideal output signals. Typical units are kelvin. Sometimes this is quoted as

a fraction of the full-scale output or a fraction of the reading. For example, a

thermometer might be guaranteed accurate to within 5% of FSO (Full Scale

Output). “Accuracy” is generally considered by metrologists to be a qualitative

term, while “uncertainty” is quantitative. For example one sensor might have

better accuracy than another if its uncertainty is 1% compared to the other

with an uncertainty of 3%.

Hysteresis

Some sensors do not return to the same output value when the input stimulus

is cycled up or down. The width of the expected error in terms of the measured

quantity is defined as the hysteresis. Typical units are kelvin or percent of FSO.

Nonlinearity (often called Linearity)

The maximum deviation from a linear transfer function over the specified

dynamic range. There are several measures of this error. The most common

compares the actual transfer function with the “best straight line,” which lies

midway between the two parallel lines that encompass the entire transfer func￾tion over the specified dynamic range of the device. This choice of comparison

method is popular because it makes most sensors look the best. Other refer￾ence lines may be used, so the user should be careful to compare using the

same reference.

Noise

All sensors produce some output noise in addition to the output signal. In

some cases, the noise of the sensor is less than the noise of the next element

in the electronics, or less than the fluctuations in the physical signal, in which

case it is not important. Many other cases exist in which the noise of the

sensor limits the performance of the system based on the sensor. Noise is gen￾erally distributed across the frequency spectrum. Many common noise sources

produce a white noise distribution, which is to say that the spectral noise

density is the same at all frequencies. Johnson noise in a resistor is a good ex￾ample of such a noise distribution. For white noise, the spectral noise density

is characterized in units of volts/Root (Hz). A distribution of this nature adds

noise to a measurement with amplitude proportional to the square root of the

measurement bandwidth. Since there is an inverse relationship between the

bandwidth and measurement time, it can be said that the noise decreases with

the square root of the measurement time.