26 CHAPTER 3: Measurement Issues and Criteria ...29 CHAPTER 4: Sensor Signal Conditioning ...31 4.1 Conditioning Bridge Circuits .... 571 CHAPTER 22: Wireless Sensor Networks: Principles
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Trang 3Sensor Technology Handbook
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Trang 5Sensor Technology Handbook
Editor-in-Chief Jon S Wilson
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Trang 6Newnes is an imprint of Elsevier
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Trang 7Preface 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
Trang 8Contents
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
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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
Trang 10CHAPTER 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
Trang 11Preface
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 tions Tremendous advances have been made in sensor technology and many more are
applica-on the horizapplica-on
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, facing and signal conditioning is given for each sensor type
inter-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
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Trang 13C 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 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
instruc-However, there are many formats in existence, and there is nothing close to an ternational standard for sensor specifications The system designer will encounter a variety of interpretations of sensor performance parameters, and it can be confusing
in-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
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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:
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 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
Trang 15Hysteresis
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
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