Sensors and actuators : Engineering System Instrumentation

831 Pages·2015·10.65 MB·English

by  De Silva

S e c o n d E d i t i o n
S E N S O R S
a n d
A C T U A T O R S
ENGINEERING SYSTEM INSTRUMENTATION
S e c o n d E d i t i o n
S E N S O R S
a n d
A C T U A T O R S
ENGINEERING SYSTEM INSTRUMENTATION
Clarence W. de Silva
Boca Raton London New York
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To Charmaine, CJ, and Cheryl, as they explore the world with their
sensors and actuators from an increasingly mature perspective.
But as artificers do not work with perfect accuracy, it comes to pass that mechanics is so distinguished
from geometry that what is perfectly accurate is called geometrical; what is less so, is called mechani-
cal. However, the errors are not in the art, but in the artificers.
Sir Isaac Newton, Principia Mathematica,
Cambridge University, May 8, 1686
TThhiiss ppaaggee iinntteennttiioonnaallllyy lleefftt bbllaannkk
Contents
Preface.....................................................................................................................xix
Units and Conversions (Approximate) ...............................................................xxiii
Acknowledgments .................................................................................................xxv
Author ..................................................................................................................xxvii
1 Instrumentation of an Engineering System
Chapter Highlights ........................................................................................................................................1
1.1 Role of Sensors and Actuators .........................................................................................................1
1.1.1 Importance of Estimation in Sensing ............................................................................3
1.1.2 Innovative Sensor Technologies ......................................................................................4
1.2 Application Scenarios ......................................................................................................................4
1.3 Human Sensory System ...................................................................................................................6
1.4 Mechatronic Engineering ................................................................................................................7
1.4.1 Mechatronic Approach to Instrumentation ..................................................................8
1.4.2 Bottlenecks for Mechatronic Instrumentation .............................................................8
1.5 Control System Architectures ........................................................................................................9
1.5.1 Feedback and Feedforward Control ..............................................................................11
1.5.2 Digital Control ..................................................................................................................13
1.5.3 Programmable Logic Controllers ..................................................................................14
1.5.3.1 PLC Hardware. ................................................................................................16
1.5.4 Distributed Control ..........................................................................................................16
1.5.5 Hierarchical Control ........................................................................................................17
1.6 Instrumentation Process ................................................................................................................18
1.6.1 Instrumentation Steps .....................................................................................................19
1.6.2 Application Examples .....................................................................................................20
1.6.2.1 Networked Application ................................................................................20
1.6.2.2 Telemedicine System .....................................................................................22
1.6.2.3 Homecare Robotic System ...........................................................................25
1.6.2.4 Water Quality Monitoring ...........................................................................26
1.7 Organization of the Book ..............................................................................................................27
Summary Sheet ...........................................................................................................................................29
Problems .......................................................................................................................................................31
v
vi Contents
2 Component Interconnection and Signal Conditioning
Chapter Highlights .....................................................................................................................................35
2.1 Introduction ....................................................................................................................................35
2.1.1 Component Interconnection .........................................................................................35
2.1.2 Signal Modification and Conditioning ........................................................................37
2.1.3 Chapter Overview ...........................................................................................................37
2.2 Impedance .......................................................................................................................................38
2.2.1 Definition of Impedance ................................................................................................38
2.2.2 Importance of Impedance Matching in Component Interconnection ...................38
2.3 Impedance Matching Methods ....................................................................................................39
2.3.1 Maximum Power Transfer .............................................................................................40
2.3.2 Power Transfer at Maximum Efficiency ......................................................................42
2.3.3 Reflection Prevention in Signal Transmission ............................................................42
2.3.4 Loading Reduction ..........................................................................................................44
2.3.4.1 Cascade Connection of Devices ..................................................................44
2.3.4.2 Impedance Matching for Loading Reduction ...........................................48
2.3.5 Impedance Matching in Mechanical Systems ............................................................48
2.3.5.1 Vibration Isolation ........................................................................................48
2.3.5.2 Mechanical Transmission ............................................................................55
2.4 Amplifiers ........................................................................................................................................58
2.4.1 Operational Amplifier ....................................................................................................59
2.4.1.1 Differential Input Voltage ............................................................................60
2.4.2 Amplifier Performance Ratings .....................................................................................61
2.4.2.1 Common-Mode Rejection Ratio .................................................................63
2.4.2.2 Use of Feedback in Op-Amps ......................................................................65
2.4.3 Voltage, Current, and Power Amplifiers ......................................................................65
2.4.4 Instrumentation Amplifiers ...........................................................................................68
2.4.4.1 Differential Amplifier ...................................................................................69
2.4.4.2 Instrumentation Amplifier ..........................................................................70
2.4.4.3 Common Mode ..............................................................................................70
2.4.4.4 Charge Amplifier ............................................................................................71
2.4.4.5 AC-Coupled Amplifiers ................................................................................72
2.4.5 Noise and Ground Loops ...............................................................................................72
2.4.5.1 Ground-Loop Noise ......................................................................................72
2.5 Analog Filters ..................................................................................................................................73
2.5.1 Passive Filters and Active Filters ...................................................................................76
2.5.1.1 Number of Poles ............................................................................................76
2.5.2 Low-Pass Filters ...............................................................................................................76
2.5.2.1 Low-Pass Butterworth Filter ........................................................................79
2.5.3 High-Pass Filters ..............................................................................................................84
2.5.4 Band-Pass Filters .............................................................................................................86
2.5.4.1 Resonance-Type Band-Pass Filters .............................................................87
2.5.5 Band-Reject Filters ..........................................................................................................90
2.5.6 Digital Filters .....................................................................................................................91
2.5.6.1 Software Implementation and Hardware Implementation.....................93
2.6 Modulators and Demodulators ....................................................................................................93
2.6.1 Amplitude Modulation ...................................................................................................96
2.6.1.1 Analog, Discrete, and Digital AM ..............................................................96
2.6.1.2 Modulation Theorem ....................................................................................96
2.6.1.3 Side Frequencies and Sidebands ..................................................................97
Contents vii
2.6.2 Application of Amplitude Modulation ........................................................................98
2.6.2.1 Fault Detection and Diagnosis ...................................................................100
2.6.3 Demodulation .................................................................................................................100
2.6.3.1 Advantages and Disadvantages of AM .....................................................101
2.6.3.2 Double Sideband Suppressed Carrier ........................................................102
2.6.3.3 Analog AM Hardware .................................................................................102
2.7 Data Acquisition Hardware .........................................................................................................104
2.7.1 Digital-to-Analog Converter ........................................................................................108
2.7.1.1 DAC Operation .............................................................................................109
2.7.2 Analog-to-Digital Converter ........................................................................................113
2.7.2.1 Successive Approximation ADC ................................................................114
2.7.2.2 Delta–Sigma ADC ........................................................................................115
2.7.2.3 ADC Performance Characteristics ............................................................116
2.7.3 Sample-and-Hold Hardware.........................................................................................118
2.7.4 Multiplexer ......................................................................................................................119
2.7.4.1 Analog Multiplexers .....................................................................................120
2.7.4.2 Digital Multiplexers .....................................................................................121
2.8 Bridge Circuits ...............................................................................................................................122
2.8.1 Wheatstone Bridge .........................................................................................................123
2.8.2 Constant-Current Bridge ..............................................................................................125
2.8.3 Hardware Linearization of Bridge Outputs ...............................................................127
2.8.3.1 Bridge Amplifiers .........................................................................................127
2.8.4 Half-Bridge Circuits .......................................................................................................128
2.8.5 Impedance Bridges .........................................................................................................129
2.8.5.1 Owen Bridge ..................................................................................................130
2.8.5.2 Wien-Bridge Oscillator ................................................................................131
2.9 Linearizing Devices .......................................................................................................................131
2.9.1 Nature of Nonlinearities ...............................................................................................131
2.9.1.1 Linearization Methods ................................................................................132
2.9.1.2 Linearization by Software ...........................................................................133
2.9.1.3 Linearization by Logic Hardware ..............................................................134
2.9.2 Analog Linearizing Hardware ......................................................................................135
2.9.2.1 Offsetting Circuitry......................................................................................136
2.9.2.2 Proportional-Output Hardware .................................................................137
2.9.2.3 Curve-Shaping Hardware ...........................................................................138
2.10 Miscellaneous Signal-Modification Hardware .........................................................................139
2.10.1 Phase Shifters ..................................................................................................................139
2.10.1.1 Applications ..................................................................................................140
2.10.1.2 Analog Phase Shift Hardware .....................................................................140
2.10.1.3 Digital Phase Shifter .....................................................................................141
2.10.2 Voltage-to-Frequency Converters ................................................................................142
2.10.2.1 Applications ..................................................................................................143
2.10.2.2 VFC Chips .....................................................................................................143
2.10.3 Frequency-to-Voltage Converter ..................................................................................144
2.10.4 Voltage-to-Current Converter ......................................................................................145
2.10.5 Peak-Hold Circuits .........................................................................................................146
Summary Sheet ..........................................................................................................................................147
Problems .....................................................................................................................................................151
viii Contents
3 Performance Specification and Instrument Rating Parameters
Chapter Highlights ....................................................................................................................................167
3.1 Performance Specification ...........................................................................................................167
3.1.1 Parameters for Performance Specification .................................................................168
3.1.1.1 Performance Specification in Design and Control .................................169
3.1.1.2 Perfect Measurement Device ......................................................................169
3.1.2 Dynamic Reference Models ..........................................................................................170
3.1.2.1 First-Order Model ........................................................................................170
3.1.2.2 Simple Oscillator Model ..............................................................................172
3.2 Time-Domain Specifications .......................................................................................................172
3.2.1 Stability and Speed of Response ...................................................................................174
3.3 Frequency-Domain Specifications ..............................................................................................176
3.3.1 Gain Margin and Phase Margin ..................................................................................178
3.3.2 Simple Oscillator Model in Frequency Domain ........................................................179
3.4 Linearity ..........................................................................................................................................180
3.4.1 Linearization ...................................................................................................................183
3.5 Instrument Ratings .......................................................................................................................184
3.5.1 Rating Parameters ..........................................................................................................185
3.5.2 Sensitivity ........................................................................................................................185
3.5.2.1 Sensitivity in Digital Devices .....................................................................186
3.5.2.2 Sensitivity Error ............................................................................................187
3.5.2.3 Sensitivity Considerations in Control .......................................................187
3.6 Bandwidth Analysis ......................................................................................................................195
3.6.1 Bandwidth .......................................................................................................................195
3.6.1.1 Transmission Level of a Band-Pass Filter .................................................196
3.6.1.2 Effective Noise Bandwidth ..........................................................................196
3.6.1.3 Half-Power (or 3 dB) Bandwidth................................................................196
3.6.1.4 Fourier Analysis Bandwidth .......................................................................197
3.6.1.5 Useful Frequency Range ..............................................................................198
3.6.1.6 Instrument Bandwidth ................................................................................198
3.6.1.7 Control Bandwidth ......................................................................................198
3.6.2 Static Gain ......................................................................................................................200
3.7 Aliasing Distortion Due to Signal Sampling .............................................................................201
3.7.1 Sampling Theorem ........................................................................................................202
3.7.2 Another Illustration of Aliasing .................................................................................202
3.7.3 Antialiasing Filter ..........................................................................................................203
3.7.4 Bandwidth Design of a Control System .....................................................................207
3.7.4.1 Comment about Control Cycle Time .......................................................208
3.8 Instrument Error Considerations ..............................................................................................209
3.8.1 Error Representation .....................................................................................................209
3.8.1.1 Instrument Accuracy and Measurement Accuracy ................................210
3.8.1.2 Accuracy and Precision ...............................................................................210
3.9 Error Propagation and Combination .........................................................................................211
3.9.1 Application of Sensitivity in Error Combination ......................................................212
3.9.2 Absolute Error .................................................................................................................213
3.9.3 SRSS Error .......................................................................................................................213
3.9.4 Equal Contributions from Individual Errors .............................................................214
Summary Sheet ..........................................................................................................................................219
Problems ....................................................................................................................................................223