Tài liệu Wireless Sensors and Instruments P1 ppt

Wireless sensors and instruments : networks, design, and applications / Halit Eren.. Instrumentation requires a broad knowledge involving a diverse range ofdisciplines, such as measureme

A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.

Wireless Sensors and Instruments

Networks, Design, and Applications Halit Eren

Boca Raton London New York

Published in 2006 by

CRC Press

Taylor & Francis Group

6000 Broken Sound Parkway NW, Suite 300

Boca Raton, FL 33487-2742

© 2006 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group

No claim to original U.S Government works

Printed in the United States of America on acid-free paper

10 9 8 7 6 5 4 3 2 1

International Standard Book Number-10: 0-8493-3674-0 (Hardcover)

International Standard Book Number-13: 978-0-8493-3674-4 (Hardcover)

Library of Congress Card Number 2005050502

This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use.

No part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400 CCC is a not-for-profit organization that provides licenses and registration for a variety of users For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged

Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only

for identification and explanation without intent to infringe.

Library of Congress Cataloging-in-Publication Data

Eren, Halit, Ph D.

Wireless sensors and instruments : networks, design, and applications / Halit Eren.

p cm

Includes bibliographical references and index

ISBN 0-8493-3674-0 (alk paper)

1 Wireless communication systems Design and construction 2 Electronic instruments Design and construction 3 Sensor networks Design and construction I Title.

TK5103.2.E74 2005

Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

Taylor & Francis Group

is the Academic Division of Informa plc.

3674_Discl.fm Page 1 Monday, October 10, 2005 1:23 PM

Dedicated to Semra, Ahmet, Suheyla, and Duygu

3674_C000.fm Page v Tuesday, October 4, 2005 8:54 AM

The evolutionary tree representing the growth of instruments and mentation technology is marked by a major fork One branch is representingstand-alone instruments fulfilling the tasks of the requirements of dedicatedmeasurements Another branch is represented by instruments that can benetworked to cooperatively work with many others to measure the variables

instru-of complex systems Neither instru-of these branches is new What is new is thatthe networking of instruments can be done without the need for physicalhard-wired connections Wireless connectivity and networkability opens upmany possibilities of research, development, and applications that we couldnot even dream of in the near past Instruments can now be networked bynew and novel techniques while they are on the move in their individualenvironments performing their tasks

Many of us are very familiar with a number of wireless devices rangingfrom mobile and cordless telephones, pagers, garage door openers, remotecontrollers, home entertainment equipment controllers, and so on The pro-liferation of wireless systems in consumer products and industrial applica-tions is so fast that a progressive involvement in technology development

is vital for many governments and industrial establishments to maintaincompetitiveness This book will be helpful to highlight the expansion ofwireless systems in instrumentation and measurements

Instrumentation requires a broad knowledge involving a diverse range ofdisciplines, such as measurement science, design and construction of elec-tronic circuits, understanding of IC technology, appreciation of theory andpractice of wireless communication systems, networks, protocols, and stan-dards This book is specifically written to provide sufficient knowledge toenable the readers to understand the underlying principles in wireless instru-mentation and networks Particular emphasis is given to the wireless com-munication systems since it is an important area of science and technologythat is expanding very rapidly thus impacting all aspects of our daily lives

It is also one of the most promising areas of research and development Wireless communication technologies have become very popular and thereare hundreds of wireless equipment manufacturers and perhaps as manystandards Understanding the benefits and shortfalls of each equipment andassociated standards can make the selection and implementation easier Inthis respect this book provides guidance to state-of-art of wireless technology

as it offers many benefits in measurement applications Some of the benefitscan be lowering the wiring costs, simplifying data transfer, extending thedistance of communication, enabling remote monitoring, and providing flex-ibility in the networking of the devices

3674_C000.fm Page vii Tuesday, October 4, 2005 8:54 AM

The purpose of Wireless Sensors and Instruments: Networks, Design, and Applications is to provide knowledge and guidance for engineers, scientists,designers, researchers, and students who are involved in measurement andinstrumentation This book covers concepts in instruments and instrumen-tation, electromagnetic wave propagation, radio engineering, digital net-works, wireless sensors and instruments design and applications Eachchapter includes descriptive information for professionals, students, andtechnical staff involved in measurement and control Numerous equationsare given to assist engineers and scientists who wish to solve problems thatarise in a fields other than their specialties

3674_C000.fm Page viii Tuesday, October 4, 2005 8:54 AM

Many people have directly and indirectly contributed to this book I thankthe people, colleagues and those whose paths I have crossed during myworking life My particular thanks are to Professor Kit Po Wong at HongKong Polytechnic University for providing encouragement to go ahead withthis book while I was appointed visiting professor at his institution Writingbooks is a lonely affair requiring major commitments and a great deal ofpatience and determination The encouragement of Kit Po has beenextremely valuable when I needed it most I would like to thank my col-leagues at Gazi University, Department of Electrical and Computer Engi-neering, Ankara, for providing an office and computer facilities in the initialand final stages of writing

I would like to thank all the companies that provided information on theirproducts and granted permission to reprint some of the images of theirequipment In particular my appreciations are extended to Steven Arms ofMicrostrain Inc.; Wayne Magnes of Oak Ridge National Laboratory; GrahamMoss of Elprotech; Randy Culpepper of Texas Instruments; Colleen Cronin

of Analog Devices, Inc.; Colin Pickard of Oregon Scientific; and Shana Jacob

of CrossBow Inc

Special thanks are extended to the CRC Press staff who made this bookpossible, especially to Nora Konopka for guiding the book through comple-tion; also thanks to Helena Redshaw, Manager of Editorial Project develop-ment; and Jay Margolis, Project Editor, for their patient and professionalinvolvements in putting it all together

3674_C000.fm Page ix Tuesday, October 4, 2005 8:54 AM

Halit Eren, Ph.D., received the B.Eng degree in 1973, the M.Eng degree inelectrical engineering in 1975 and the PhD degree in control engineeringfrom the University of Sheffield UK He earned an MBA from Curtin Uni-versity of Technology, Western Australia in 1998 majoring in internationalmanagement and leadership

Dr Eren has been lecturing at the Curtin University of Technology since

1983, first at the Kalgoorlie School of Mines and then School of Electricaland Computer Engineering, Perth, Western Australia He served as the head

of the Department of Electronic and Communication for some time

Dr Eren's expertise lies in the area of instruments, instrumentation systems,and networking; electronic portable instruments, signal processing; andengineering mathematics He has been researching in wireless and portableinstruments for more than 17 years, mainly in the areas of electromagnetic,ultrasonic and infrared techniques, fieldbus, telemetry, and telecontrollers

He serves as a consultant to many industrial and government organizations

Dr Eren has contributed to more than 150 conferences, journals and actions and various books published by the CRC Press and John Wiley &Sons

Design and Applications published by the CRC Press in 2004 This secondbook on wireless sensors and instruments networks, design and applicationsforms a synergy with the first book as the application of modern technology

is producing a large number of portable and wireless instruments

3674_C000.fm Page xi Tuesday, October 4, 2005 8:54 AM

Instruments are essential for measuring physical variables in industrial ations, consumer products, environmental monitoring, research and devel-opment (R&D), transportation, military, space exploration, avionics, and so

oper-on A collection of instruments form an instrumentation system, which may

be responsible for numerous measurements in a complex process ments are networked to communicate directly with each other or via inter-mediate devices such as computers, microprocessors, or controllers Today,traditional instrumentation systems communicate through wired media.However, communication between instruments by wireless techniques isdeveloping rapidly and gaining broad acceptance It is very likely that wire-less instruments will replace their wired counterparts in the very near future

Instru-In recent years, considerable progress has been made in instruments andinstrumentation systems due to the employment of integrated circuit tech-nology, analog and digital components, efficient and low-power micropro-cessors, intelligent sensors, radio frequency (RF) communication technology,and protocols and standards supporting networks In particular, cost-effec-tive RF products have expanded suddenly to unimaginable dimensions.Devices such as cellular and cordless telephones, private and public tele-phone systems, wireless modems, radio frequency identification (RFID), andwireless sensors and instruments have rapidly penetrated into all aspects ofour lives Most of these devices were initially available as rare and expensiveluxury items, but are now used by consumers, industry, and scientific andother communities With this growth in demand, small and large semicon-ductor and system vendors are competing for a larger market share byintroducing a diverse range of RF products

Most people are familiar with a number of wireless control and nication systems used in everyday life Mobile cellular telephones, cordlesstelephones, hand-held walkie-talkies, pagers, garage door openers, remotecontrollers, home entertainment equipment controllers are some of the exam-ples that can be mentioned The proliferation of wireless systems in con-sumer products and industrial applications is so fast that a progressiveinvolvement in technological developments are vital for governments andindustrial establishments alike if they want to stay competitively in therapidly changing field of wireless communication systems and their appli-cations

commu-Today’s wireless networks were largely developed for mobile telephonesand service mainly voice-based applications Nevertheless, this is changingrapidly, with great emphasis being placed on wireless data transmission andwireless access to the Internet For example, the aim of third-generation3674_C000.fm Page xiii Tuesday, October 4, 2005 8:54 AM

wireless systems, which provide access to the Internet, video, etc., is to makepersonal communication available anywhere at any time Similarly, theapplication of wireless techniques to measurement and instrumentation isenabling configuration of wireless instrumentation networks in many appli-cations, ranging from intelligent buildings to implantable wireless sensorsused for human health improvement.

Wireless instrumentation requires a broad knowledge involving a diverserange of disciplines, including measurement science, design and construc-tion of electronic circuits, understanding of integrated circuit (IC) technology,appreciation of the theory and practice of wireless communication systems,networks, and protocols and standards In this book, all these concepts will

be explained sufficiently to enable readers understand the underlying ciples in wireless instrumentation and networks Particular emphasis will

prin-be placed on wireless communication systems, since it is in this area thatscience and technology are expanding Wireless communication systems arealso a promising area of research, with thousands of researchers concentrat-ing on the topic

International standards are rapidly emerging in wireless technology asapplied to sensors and instruments Some of important ones are Bluetooth,HiperLAN, and the IEEE 802 standards for communication and networks,and the IEEE 1451 family of standards for sensors These standards aregaining wide acceptance Communication among devices involved can takeplace as point-to-point or point-to-multipoint This gives considerable flex-ibility in network configuration and communication algorithms can be tai-lored to improve system reliability and adaptability

This book is a reflection of information on the latest technologies in thefield of wireless sensors, instruments, and networks Engineers and scientistswho are not trained in electrical engineering will find the book very infor-mative without overwhelming them with detailed information

This book was written for students and practicing scientists and engineerswho are already familiar with technical concepts in electronics, probabilitytheory, communication theory, basic electromagnetic theory, networks, andoperational aspects of networks However, the information given combinesmaterials from many different disciplines, therefore it is highly unlikely thatall readers will have the necessary basic knowledge for the topics covered.Therefore necessary concepts throughout the book are developed from prin-ciples to accommodate a wide range of readers from different backgrounds.This approach makes it attractive for practicing engineers and scientists whoare involved in instruments and instrumentation in their disciplines Thebook is also recommended as a useful teaching tool for undergraduate andpostgraduate students who are likely to be involved with the design andoperation of modern instruments and networks

This book contains five chapters The first three chapters provide tion on measurements, instruments, sensors, communication systems, andnetworks Information provided in these three chapters is brought together

informa-in Chapter 4 and Chapter 5

3674_C000.fm Page xiv Tuesday, October 4, 2005 8:54 AM

In Chapter 1, brief but essential background information on measurements,instruments, instrumentation, sensor technology, communication systems,and networks is given Wireless communication of instruments has beendeveloping remarkably fast and is becoming common practice in industrialand many other applications Wireless communication technology is able toaddress the needs of effective and efficient communication in all types ofinstruments and instrumentation systems Digital instruments and theirassociated theory, methods, and components are highlighted Since digitalsensor technology forms the backbone of all types of modern instruments,extensive discussions are presented on this topic Wireless instrument com-munication and its applications in industrial environments have been stud-ied It has been shown that noise, interference, and distortion can play asignificant role in the operation of instruments and their associated networks.

Chapter 2 concentrates on modern communication systems The chapterstarts with the principles of electromagnetic wave propagation and expands

to important characteristics of electromagnetic radiation, such as losses, ing, reflection, refraction, and attenuation The necessary electronic compo-nents for successful RF communication are discussed Applications of digitalcommunication techniques are making wireless sensors, instruments, andnetworks possible, thus the fundamentals of digital communication technol-ogy are explained in detail Modern communication methods, modulation,and multiplexing techniques, frequency spreading, and multiple accessmethods are also discussed and examples are given

fad-Chapter 3 discusses networks, protocols, standards, and topologies works are collections of interoperational devices linked together by a com-munication medium and supported by suitable software Networking ofhardware and software resources is essential to bring multiple devicestogether to provide efficiency by enabling the exchange of information, cre-ating collaborative operations, and sharing the functions of equipment anddevices In this chapter, the types of network topologies, protocols, andstandards relevant to wireless networks are explained The security of wire-less networks is highlighted and the methods are discussed The knowledgeand experience gained in wired network technologies can be applied directly

Net-to wireless operations Newly emerging wireless technologies such as theIEEE 802 family of standards and Bluetooth, among others, are discussed

In Chapter 4, the construction of wireless sensors and instruments is duced and examples are given Instrument communication protocols arerevisited and current technologies applied in wireless instruments and sen-sors are explained Modern wireless sensor and instrument networks canproduce using embedded or modular designs These networks can beexpanded using bridges, routers, and repeaters The construction of wirelesssensors and instruments is discussed and many examples are provided.Power issues of wireless networks are also addressed Wireless sensor net-works and wireless integrated sensor networks are detailed Applications ofBluetooth and IEEE 802 technologies are demonstrated

intro-3674_C000.fm Page xv Tuesday, October 4, 2005 8:54 AM

Chapter 5 is dedicated to the applications of wireless sensors and ments—ranging from complex industrial plants to tracking wildlife in thewilderness New application areas are being added as vendors of wirelesssensors and instruments respond to consumer demands by offering a diverserange of wireless devices In this chapter, examples of wireless sensors,instruments, and networks are provided in the following areas: specificapplications, commercial applications, R&D, industrial applications, humanhealth, environmental applications, RFID, consumer products, and otherapplications.

instru-This book reflects the current state of the art in wireless sensors andinstrument technology and provides guidance to students, researchers, prac-ticing engineers, and scientists I hope you enjoy it, as well as gain valuableknowledge from it, so that you can put this knowledge in use in the area ofyour interest

3674_C000.fm Page xvi Tuesday, October 4, 2005 8:54 AM

Table of Contents

1 Instruments and Instrumentation 1

1.1 Measurements 2

1.2 Instrument Architecture and Instrumentation 3

1.2.1 Signals and Signal Conditioning 3

1.2.2 Types of Instruments 6

1.3 Digital Instrument Hardware and Software 8

1.3.1 Components of Digital Instruments 10

1.3.2 Microprocessors and Microcontrollers 11

1.3.3 Input and Output 14

1.3.4 Signal Conversion 15

1.3.5 Digital Signal Processing 20

1.4 Sensor Technology and Advanced Sensors 21

1.4.1 Sensing Materials 21

1.4.2 Process of Developing Sensors 24

1.4.3 Trends in Sensor Technology and IC Sensors 25

1.4.4 Sensor Arrays and Multisensor Systems 28

1.4.5 Smart Sensors 29

1.5 Instrument and Sensor Communication and Networks 32

1.5.1 Wireless Instrument Communication 33

1.5.2 Modulation and Coding of Instrument Signals 35

1.5.3 Example of Wireless Communication Systems 37

1.5.4 Examples of Wireless Sensors and Instruments 38

1.6 Industrial Instrumentation Systems 38

1.6.1 Industrial Communication Networks 40

1.6.2 Basic Elements of Industrial Sensor Networking 41

1.6.3 Industrial Network Protocols 42

1.6.4 The Ethernet and Fieldbuses 43

1.6.5 Implementation of Fieldbuses 44

1.6.6 Design and Application Examples of Fieldbuses 46

1.6.7 Telemetry and SCADA Systems 48

1.7 Noise and Distortion 51

1.7.1 Internal Noise in Electronic Systems 51

1.7.2 Interference 54

1.7.3 Noise and Distortion in Communication Systems 55

1.7.4 Noise in Digital Systems 56

1.8 Conclusion 57

2 Wireless Communication 59

2.1 Wireless Communication Principles 60

3674_C000.fm Page xvii Tuesday, October 4, 2005 8:54 AM

2.1.1 The Decibel 60

2.2 Electromagnetic Wave Propagation 61

2.2.1 Power Aspects of Free-Space Propagating and Link Analysis 63

2.2.2 Antenna Characteristics 64

2.2.3 Near Field, Far Field, and Fading 64

2.2.4 Electrical Field Vector Addition 65

2.2.5 Free Space Path Loss 66

2.2.6 Excess Path Loss and Atmospheric Attenuation 66

2.2.7 Reflection of Electromagnetic Waves 66

2.2.8 Atmospheric Refraction 67

2.2.9 Diffraction of Electromagnetic Waves 67

2.2.10 Indoor Propagation of Electromagnetic Waves 68

2.2.11 Frequency Allocation 68

2.3 RF Components 69

2.3.1 Amplifiers 72

2.3.2 Attenuators 74

2.3.3 Filters 74

2.3.4 Oscillators 75

2.3.5 Frequency Multipliers 75

2.3.6 Mixers 76

2.3.7 Modulators and Detectors 77

2.3.8 Demodulators 80

2.3.9 Multiplexers 82

2.3.10 Antennas 84

2.3.11 Phase Detectors and Phase Shifters 85

2.3.12 Power Dividers and Power Combiners 86

2.3.13 RF Transformers 86

2.3.14 EMI and RFI Filters 87

2.3.15 Other Components 88

2.3.16 RF Transceivers 88

2.3.17 Wireless Modems 89

2.4 Analog Modulation and Multiplexing 90

2.4.1 Amplitude Modulation 91

2.4.2 Frequency Modulation 93

2.4.3 Phase Modulation 95

2.4.4 Frequency and Time Division Multiplexing 95

2.5 Digital Modulation and Multiplexing 96

2.5.1 Amplitude Shift Keying 97

2.5.2 Frequency Shift Keying 97

2.5.3 Phase Shift Modulation 98

2.5.4 Binary Phase Shift Keying 98

2.5.5 Differential Phase Shift Keying 99

2.5.6 Quaternary Phase Shift Keying 100

2.5.7 Offset QPSK 102

2.5.8 Differential QPSK 103

3674_C000.fm Page xviii Tuesday, October 4, 2005 8:54 AM

2.5.9 Octonary Phase Shift Keying 104

2.5.10 Digital Multiplexing 104

2.6 Frequency Spreading and Multiple Access Techniques 104

2.6.1 Direct Sequence Spread Spectrum 106

2.6.2 Frequency Hopped Spread Spectrum 110

2.6.3 Multiple Access Techniques 112

2.6.4 Frequency Division Multiple Access 114

2.6.5 Time Division Multiple Access 114

2.6.6 Spread Spectrum Multiple Access 117

2.6.7 Code Division Multiple Access 117

2.6.8 Frequency Hopped Multiple Access 118

2.6.9 Hybrid Spread Spectrum Techniques 119

2.6.10 Space Division Multiple Access 120

2.6.11 Carrier Sense Multiple Access 121

2.6.12 Packet Radio 122

2.7 Conclusion 123

3 Data Transfer, Networks, Protocols, and Standards 125

3.1 Data Transfer 126

3.1.1 Serial and Parallel Data Transmission 127

3.1.2 Synchronous and Asynchronous Transmission 127

3.1.3 Simplex, Half-Duplex, and Full-Duplex Data Transmission 130

3.1.4 Wireless Data Transmission 131

3.1.5 Radio Frequency Data Transmission 131

3.1.6 Infrared Data Transmission 132

3.1.7 Microwave Data Transmission 133

3.2 Security in Data Flow 133

3.2.1 Channel Coding 134

3.2.2 Encryption 136

3.3 Network Essentials and Topologies 138

3.3.1 Network Software 139

3.3.2 Network Topologies 140

3.3.3 Internetworking 143

3.3.4 Internet and Intranet 145

3.4 Protocols 146

3.4.1 The OSI model 147

3.4.2 Structure of the OSI Model 148

3.4.3 IEEE 802 Network Model 152

3.5 Standards 153

3.5.1 IEEE 802 Standards 155

3.5.2 Wireless Ethernet Concepts 156

3.5.3 IEEE 802.16 Wireless Metropolitan Area Networks 157

3.5.4 Code Division Multiple Access-Based Standards 158

3.5.5 Time Division Multiple Access-Based Standards 158

3674_C000.fm Page xix Tuesday, October 4, 2005 8:54 AM

3.5.6 GSM and GPRS Standards 159

3.5.7 Other Wireless Network Standards 160

3.5.8 IEEE 1451 Standards for Smart Sensor Interface 160

3.6 Wireless Networks, PANs, LANs, and WLANs 163

3.6.1 Recent Developments in Frequency Allocation 165

3.6.2 Types of Wireless Networks 166

3.6.3 Wireless Network Topologies 167

3.6.4 Wireless Extended LAN Technologies 167

3.6.5 IEEE 802.11 WLAN Standards 167

3.6.6 The HiperLAN Standard 169

3.6.7 Bluetooth 170

3.6.8 Industrial Sensor Buses and Networks 172

3.7 Network, Data, and Information Management 176

3.7.1 Network Management 176

3.8 Conclusion 177

4 Wireless Instrument and Sensor Networks 179

4.1 Wireless Sensor Architecture and Network Design 180

4.1.1 Wireless Sensors and Transducers 181

4.1.2 Architecture of Wireless Sensor Networks 188

4.1.3 Effect of IEEE 1451 Standards on Sensor Networks 190

4.2 Wireless Instrument Architecture and Network Design 191

4.2.1 Essential Components of Wireless Instruments 194

4.2.2 Wireless Bridges, Routers, Gateways, and Repeaters 196

4.2.3 Wireless Data Loggers 198

4.2.4 Power Considerations of Wireless Instruments 199

4.2.5 Other Wireless Instrument Issues 202

4.3 Wireless Sensor and Instrument Network Design 206

4.3.1 Mobile Wireless Instrument and Sensor Networks 208

4.3.2 Energy Issues in Wireless Sensor Networks 211

4.3.3 Bluetooth Sensor Networks 212

4.3.4 Applications of Bluetooth Networks 215

4.3.5 IEEE 802 Sensor and Instrument Networks 217

4.4 Wireless Integrated Network Sensors 219

4.4.1 Power Requirements in WINS 222

4.4.2 Application of WINS 224

4.5 Plug-and-Play Sensors and Networks 225

4.5.1 Bluetooth and Plug-and-Play Sensor Networks 227

4.6 Industrial Wireless Networks and Automation 228

4.6.1 Wireless Fieldbuses 229

4.6.2 Wireless Industrial Mesh Networks 230

4.7 Conclusion 233

5 Wireless Sensor and Instrument Applications 235

5.1 Application-Specific Wireless Sensors and Instruments 235

3674_C000.fm Page xx Tuesday, October 4, 2005 8:54 AM

5.1.1 Application-Specific Wireless Sensors and Networks 237

5.1.2 Application-Specific Embedded Wireless Instruments and Networks 238

5.1.3 Application-Specific Modular and Add-On Wireless Instruments and Networks 241

5.2 Commercial Wireless Sensors and Instruments 245

5.3 Wireless Instruments and Sensor Networks in Research and Development 248

5.3.1 Hardware and Software Issues at the Operational and Physical Level 248

5.3.2 Efficiency at the Physical and Network Level 251

5.3.3 Issues on Communication Protocols and Network Management 253

5.4 Industrial Wireless Sensor and Instrument Networks 255

5.4.1 Integration of Wireless Systems to Fieldbuses 258

5.4.2 Wireless Built-in Tests and Condition–Based Maintenance 264

5.5 Wireless Human Health Monitoring and Environmental Applications 266

5.5.1 Wireless Human Health Systems 267

5.5.2 Wireless Environmental and Habitat Monitoring Systems 270

5.5.3 Environmental Observation and Forecasting Systems 272

5.6 Radio Frequency Identification 274

5.7 Consumer Products and Other Applications 278

5.7.1 Wireless Consumer Products 278

5.7.2 Other Wireless Applications 280

5.8 Conclusion 283

Bibliography 285

3674_C000.fm Page xxi Tuesday, October 4, 2005 8:54 AM

1

Instruments and Instrumentation

Instruments are developed for sensing and measuring physical variables thatare essential in industrial operations, environmental applications, researchand development (R&D), transportation, military equipment, and in ourdaily lives Instrumentation systems are collections of instruments net-worked to communicate with each other directly or via some intermediatedevice such as computers or microprocessors The majority of instrumentcommunication systems have been based on wired media, but today wirelesscommunication is developing rapidly and becoming common in industrialand many other applications In this chapter, brief but essential backgroundinformation is provided on measurements, instruments, instrumentation,sensor technology, communication systems, and networks

If the behavior of the physical variable is known, its performance can bemonitored and assessed Applications of instruments range from laboratoryconditions to arduous environments, such as inside nuclear reactors, toremote locations, such as satellite systems or spaceships Manufacturersproduce a wide range of instruments in order to meet diverse requirements.The majority of modern instruments have a great degree flexibility in theirrange of uses, types of displays, and methods of communication with otherdevices

In instrument communication, information generated by a source is passed

to a sink The source converts the measured or sensed variable into electricalsignals Electrical signals are then processed and modified into communica-tion signals that are passed through a communication channel in the form

of useful information or a message The received signals are then convertedback into signals at the sink Information can be transmitted through wired

or wireless media by a variety of techniques

In recent years, considerable progress has been made in measurements,instruments, and instrumentation systems because of the progress in inte-grated circuit (IC) technology, the availability of low cost analog and digitalcomponents, and efficient microprocessors Consequently the performance

of measuring and monitoring instruments has improved significantlybecause of the availability of on-line and off-line analysis, advanced signalprocessing techniques, and local and international standards Today’s wire-less communication technology is able to address the needs of effective and3674_C001.fm Page 1 Monday, October 10, 2005 1:07 PM

2 Wireless Sensors and Instruments

efficient communication in all types of instruments and instrumentationsystems

In this chapter, measurement issues are introduced and instrument tecture explained Digital instruments and their associated theory, methods,and components are highlighted Sensor technology is the backbone of alltypes of instruments, therefore sensors will be explained in detail A generalintroduction is provided on instrument communication as applied to com-mon instruments as well as those used in industry Instrument networks andtheir associated standards and protocols are discussed Overall, this chapterconcentrates on the source and associated issues such as noise, distortion,and interference during communication

Measurement is a process of gathering information from the physical worldwithin agreed upon national and international standards and procedures.Measurements are carried out using manmade instruments that are designedand manufactured to perform specific functions The functionality of aninstrument is to maintain a prescribed relationship between the measurednumerical values and the physical variable, or measurand, under investiga-tion

A typical instrument has many components, the sensors and transducersbeing the primary elements that respond to the physical variable and gen-erate useful signals A sensor is a physical entity that converts a physicalvariable into a processable electrical signal Sensor signals in the majority ofmodern instruments are in electrical form or they are ultimately converted

to an electrical form This is because electrical signals are easy to process,display, store, and transmit Similar to sensors, transducers also convertenergy from one form to another between two physical systems

Transducers are used in a wide variety of industries, including aerospace,automotive, biomedical, industrial control, manufacturing, and process con-trol As the demand for automation systems grows, the need for transducersincreases This demand is partially met by the development of smart sensorsand transducers and by the integration of wireless technologies, makingtoday’s instruments and instrumentation systems much more flexible,cheaper, and easer to use

Once converted to electrical form, the relation between the sensor signalsand physical variations can be expressed in a transfer function, a mathemat-ical model between the sensor signal and the physical variable In a contin-uous system, the transfer function may be linear or nonlinear For example,

a linear relationship is expressed by the following equation:

3674_C001.fm Page 2 Monday, October 10, 2005 1:07 PM

Instruments and Instrumentation 3

fre-quencies, phases, or other properties of electrical signals, depending on thedesign and construction of a particular sensor and the nature of the variable.The nonlinear transfer functions can be logarithmic, exponential, or in otherforms of mathematical functions In many applications, a nonlinear sensorsignal may be linearized over some limited ranges

For a specific measurement, a wide range of sensors and transducers may

be available Selection of the correct sensors, transducers, and components

to retrieve the required information and employment of representative signalprocessing techniques is essential

Instruments are manmade devices that are designed and constructed usingthe existing knowledge about a physical process and the available technol-ogy Appropriate hardware and software are engineered that can performwell within the expected specifications and standards

The functionality of a typical instrument can be broken into smaller

or all of these components Instruments differ from each other in the waythey handle, transmit, and display information

Generally signals from sensors are not suitable for displaying, recording,

or transmitting in their raw form The amplitudes, power levels, or widths of sensor signals may be very small or may carry excessive noise andsuperimposed interference that masks the desired components Signal con-ditioners adapt sensor signals to acceptable levels and shapes for processingand display

band-1.2.1 Signals and Signal Conditioning

Measurement of physical variables generally leads to the generation cal signals A signal can be defined as “any physical quantity that varieswith time, space, or any other independent variable or variables.” Naturally,different types of signals require different processing techniques, hence dif-ferent types of analog and digital methods must be used and associatedcomponents must be selected

electri-The analysis and processing of signals requires some kind of mathematicaldescription of the signal A signal can be described as a function of one ormore independent variables Therefore signals generated by sensors can be3674_C001.fm Page 3 Monday, October 10, 2005 1:07 PM

4 Wireless Sensors and Instruments

classified in a number of mathematical ways, such as multichannel andmultidimensional signals, continuous time or discrete signals, deterministic

or random (stationary, nonstationary) signals, transient signals, etc

In some applications where multiple signal sources are present, multiplesensors are used to generate signals These signals can be represented invectors Generally if the signal is a function of a single independent variable,

signals picked by various accelerometers) Vectors in matrix form can resent such signals, and appropriate techniques are applied for processing.Any signal that can be expressed by an explicit mathematical expression

rep-or by well-defined rules is called a deterministic signal That is, the past,present, and future value of the signal is known precisely without uncer-tainty In this respect, the signal may be classified according to the charac-teristics of an independent variable (e.g., time) and the value it takes.Deterministic signals can be continuous or discrete

Continuous signals, also known as analog signals, are defined for every

nonpe-riodic In periodic signals, the signal repeats itself in an oscillatory manner,which can be represented as a sinusoidal waveform:

Continuous signals can be periodic, but not necessarily sinusoidal, such

as triangular, sawtooth, rectangular, or other regular or irregular shapes Ifthe signals are periodic but nonsinusoidal, they can be expressed in Fourierseries as a combination of a number of pure sinusoidal waveforms as

angles

In Equation 1.3, the number of terms may be infinite, and the greater thenumber of elements the better the approximation These elements constitutethe frequency spectrum The signals can be represented in the time domain

or frequency domain, both of which are extremely useful in the analysis

and Transducer

Signal conditioner

Signal processing

Transmission and/or Display

3674_C001.fm Page 4 Monday, October 10, 2005 1:07 PM