Data Acquisition for Sensor Systems

332 Pages·1997·7.62 MB·English

by  H. Rosemary Taylor (auth.)

Data Acquisition
for Sensor Systems
Sensor Physics and Technology Series
Series editors:
Professor K. T. V. Grattan
Centre for Measurement. Instrumentation and Applied Physics
City University
London, UK
Dr A. Augousti
School of Applied Physics
Kingston University
Kingston-upon-Thames, UK
The Sensors Physics and Technology Series aims to bring together in a single series
the most important developments in the rapidly-changing area of sensor tech
nology and applications. It will present a snapshot of the range of effort which is
being invested internationally in the development of novel types of sensors. New
workers in the area of sensor technology will also be catered for with an intro
duction to the subject through the provision of tutorial guides. Volumes may be
sensor technology or applications oriented, and will present recent results from
the cutting edge of research of a compact monograph format.
Topics covered will include:
optical sensors: free-space sensors
• optical sensors: guided wave sensors
solid-state sensors
• biosensors
• microwave sensors
• ultrasonic sensors
process tomography
• control of networked sensors system control and data acquisition
medical instrumentation
• infrared sensors
• chemical and biochemical sensing
• environmental sensing
• industrial applications
Titles available:
I. Biosensors
Tran Minh Cahn
2. Fiber Optic Fluorescence Thermometry
K. T. V. Grattan and Z. Y. Zhang
3. Silicon Sensors and Circuits
F. Wolffenbuttel
4. Ultrasonic Measurements and Technologies
Stefan Kocis and Zdenko Figura
5. Data Acquisition for Sensor Systems
H. Rosemary Taylor
Data Acquisition for
Sensor Systems
H. ROSEMARY TAYLOR
formerly
Lecturer in Electrical Engineering and Electronics
at
UMIST
The University of Manchester
Institute of Science and Technology
SPRINGER-SCIENCE+BUSINESS MEDIA, B.v.
First edition 1997
© 1997 H. Rosemary Taylor
Origina1ly published by Chapman & Hali in 1997
Typeset in 10/12pt Times by Florencetype Ltd, Stoodleigh, Devon
ISBN 978-1-4419-4729-1 ISBN 978-1-4757-4905-2 (eBook)
DOI 10.10071978-1-4757-4905-2
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The publisher makes no representation, express or implied, with regard to the
accuracy of the information contained in this book and cannot accept any legal
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A catalogue record for this book is available from the British Library
Library of Congress Catalog Card Number: 96-72032
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Contents
Preface xiii
Acknowledgements xv
1 Introduction 1
1.1 What is data acquisition? 1
1.2 Elements of a data acquisition system 3
1.3 Complete data acquisition systems 4
1.3.1 Integrated circuits 4
1.3.2 Data acquisition boards 5
1.3.3 Software for data acquisition 5
1.3.4 Data loggers for process control 6
1.3.5 Digital voltmeters and multimeters 6
1.3.6 Choosing a system 6
2 Principles of measurement 9
2.1 Reasons for measuring 9
2.2 What is measurement? 9
2.2.1 Definitions and terminology 9
2.2.2 Errors and the quality of a measurement 10
2.3 Units and standards 12
2.4 Systeme Internationale d'Unites 13
2.5 Standards 13
2.6 Unit and standard of mass 15
2.7 Unit and standard of time 15
2.8 Unit and standard of length 15
2.9 Electrical units and standards 16
2.9.1 EO and fLo 16
2.9.2 Unit of electric current 16
2.9.3 Units of potential and impedance 17
2.10 Units and standards of temperature 17
2.11 Traceability and calibration 18
vi CONTENTS
3 Sensors 21
3.1 Introduction 21
3.2 Active and passive sensors 21
3.3 Effort and flow variables 22
3.4 Static performance of sensors 23
3.4.1 Accuracy 23
3.4.2 Offset 23
3.4.3 Linearity 24
3.5 Dynamic performance of sensors 25
3.5.1 First- and second-order sensors 25
3.5.2 Example of a first-order system:
a thermometer 25
3.5.3 Example of a second-order system:
a thermometer in a sheath 26
3.5.4 Example of second-order sensors:
spring-mass systems 28
3.6 Strain gauges 32
3.6.1 Description and applications 32
3.6.2 Strain 33
3.6.3 Gauge factor 35
3.6.4 Circuit layout and temperature
compensation 36
3.6.5 Signal conditioning 37
3.7 Linear variable differential transformer 37
3.8 Piezoelectric sensors 39
3.8.1 Piezoelectricity 39
3.8.2 Practical piezoelectric sensors 44
3.8.3 Ultrasonics 44
3.8.4 Frequency control 45
3.9 Temperature sensors 45
3.9.1 Platinum resistance thermometers 45
3.9.2 Signal conditioning for platinum
resistance thermometers 46
3.9.3 Thermiston 48
3.9.4 Thermocou:>les 49
3.9.5 Signal conditioning for thermocouples 50
3.9.6 Integrated circuit temperature sensors 51
3.9.7 Radiation sensors 51
3.10 Future developments 53
3.10.1 Microsensors 53
3.10.2 Smart semiors 54
3.11 Examples 54
CONTENTS vii
4 Signal conditioning 61
4.1 General 61
4.1.1 Earthing or grounding 61
4.1.2 Series and common mode noise 62
4.1.3 Errors due to common mode interference 62
4.1.4 Specification of common mode rejection
ratio 65
4.1.5 The use of a guard terminal 66
4.2 Instrumentation amplifiers 66
4.2.1 Differential gain 67
4.2.2 Common mode gain 69
4.3 Isolation amplifiers 69
4.4 Charge amplifiers 70
4.4.1 Requirements 70
4.4.2 Circuit 71
4.4.3 Frequency response 72
4.5 Filters 72
4.5.1 Classification of filters 72
4.5.2 Types of filter response 74
4.5.3 Filter circuits 78
4.6 Integrators and differentiators 81
4.7 Phase-sensitive detectors 82
4.7.1 Applications 82
4.7.2 Linear, switching PSD 83
4.7.3 Multiplying PSD 86
4.7.4 Digital PSD 87
4.7.5 Edge-triggered PSD 87
4.7.6 Phase-locked loop 87
4.8 Examples 89
5 Sample and hold circuits 95
5.1 Introduction 95
5.2 Applications 95
5.3 Slew rate and aperture error 95
5.4 Basic design 98
5.5 Operation 98
5.6 Definitions 99
5.7 Practical circuits 100
5.8 Errors 101
5.9 Choice of hold capacitor 102
5.10 Sampling converters 103
5.11 Examples 103
viii CONTENTS
6 Multiplexers 111
6.1 Introduction 111
6.2 Number of switches required 112
6.3 Reed relays 112
6.3.1 Advantages of reed relays 113
6.3.2 Disadvantages of reed relays 113
6.4 FET switches 115
6.4.1 Junction FETs (JFETs) 115
6.4.2 MOSFETs 116
6.4.3 CMOSFETs 116
6.4.4 Equivalent circuit of a JFET 116
6.5 Errors in multiplexers 118
6.6 Examples 120
7 Elements of analogue to digital and digital to
analogue converters 127
7.1 Introduction 127
7.2 Voltage references 127
7.2.1 Zener diodes 127
7.2.2 Three-terminal Zener reference devices 129
7.2.3 Bandgap references 129
7.2.4 Ratiometric measurements 132
7.3 Bipolar binary codes 132
7.3.1 Offset binary 132
7.3.2 Two's complement 132
7.3.3 Sign magnitude 133
7.3.4 Gray code 133
7.3.5 Binary coded decimal 135
7.3.6 American Standard Code for Information
Interchange 135
7.4 Examples 136
8 Digital to analogue converters 141
8.1 Design of digital to analogue converters 141
8.1.1 Weighted resistor circuit 141
8.1.2 Ladder networks 142
8.1.3 Quads 144
8.1.4 Timesharing D/As 144
8.1.5 D/A converters for digital audio 146
8.2 Bipolar DIA s 147
8.3 Multiplying D/As 147
8.4 Accuracy of D/A converters 147
CONTENTS ix
8.5 Sources of error 151
8.6 Testing DIA converters 152
8.6.1 Input codes 152
8.6.2 Step error 152
8.6.3 Dynamic testing of DIA converters 152
8.7 Examples 154
9 Analogue to digital converters 163
9.1 Early designs 163
9.2 Integrating and nonintegrating converters 165
9.3 Integrating converters 165
9.3.1 Series mode rejection ratio 167
9.3.2 Improvement of series mode rejection
ratio at mains frequency 168
9.3.3 Oversampling 168
9.3.4 Systems voltmeters 168
9.4 Dual ramp AID converter 169
9.4.1 Principle 169
9.4.2 Auto polarity using a flying capacitor 171
9.4.3 Auto-zero compensation using a flying
capacitor 171
9.4.4 Effect of delays in the switching and in the
comparator 173
9.4.5 Dielectric absorption 175
9.5 Triple ramp and multislope AID converters 177
9.6 Voltage to frequency and charge balance AID
converters 179
9.6.1 Bipolar charge balance converters 179
9.6.2 Voltage to frequency methods 179
9.6.3 Simple voltage to frequency converter 180
9.6.4 Charge balance voltage to frequency
converter 180
9.6.5 Synchronous charge balance voltage to
frequency converter 181
9.6.6 Audio sigma-delta AID converters 183
9.7 Pulse-width AID converters 185
9.8 Pulse-width, pulse-height wattmeter 186
9.9 Successive approximation AID converters 186
9.9.1 Principle 186
9.9.2 Resistive ladder converters 187
9.9.3 Sampling successive approximation
converters 188
x CONTENTS
9.10 Recirculating remainder AID converters 189
9.11 High-speed AID converters 189
9.11.1 Flash converters 189
9.11.2 Two-stage flash AID converters 192
9.12 Interfacing a converter to a microprocessor 193
9.12.1 Data transfer methods 193
9.12.2 Microprocessor-compatible converters 194
9.13 Testing AID converters 196
9.13.1 Static tests 196
9.13.2 Offset error 196
9.13.3 Gain error 196
9.13.4 Integral nonlinearity 196
9.13.5 Differential nonlinearity 197
9.13.6 Dynamic tests 197
9.13.7 Back-to-back test 197
9.13.8 Fast Fourier transform test 197
9.13.9 Beat frequency test for fast converters 198
9.13.10 Histogram test for fast converters 198
9.13.11 Other tests 198
9.14 Examples 199
10 Sampled data systems 213
10.1 Introduction 213
10.2 Sampling 213
10.3 Quantization 213
10.3.1 RMS quantization error 214
10.3.2 Signal to quantization noise ratio 215
10.4 Tracking errors 215
10.5 Aliasing errors 215
10.5.1 Theory 215
10.5.2 Aliasing errors in practice 219
10.5.3 Choice of sampling frequency 220
10.5.4 Anti-aliasing filters 221
10.6 System specification 222
10.7 Example of system design 222
10.7.1 Sensors 222
10.7.2 Signal conditioning 223
10.7.3 Linearity 223
10.7.4 Order of taking samples 223
10.7.5 Sampling rate 224
10.7.6 Timing 226
10.7.7 Transferring data to the computer 226