Advanced Interfacing Techniques for Sensors (eBook)

Preface 6
Contents 10
About the Editors 12
1 Sensors and Their Characteristics 16
Abstract 16
1 Introduction to Sensors 16
2 Sensors and Transducers 18
3 Important Characteristics of Sensors 19
3.1 Resolution of a Sensor 19
3.2 Range (Full Scale) of a Sensor 22
3.3 Safe Range (Overload Factor) of a Sensor 22
3.4 Accuracy of a Sensor 23
3.5 Gain Error, Offset and Offset Drift of a Sensor 40
3.6 Linear and Nonlinear Characteristics of a Sensor 41
3.7 Transient and Steady State Responses of a Sensor 43
3.8 Settling Time (Response Time) of a Sensor 45
3.9 Slew Rate and Rise Time of a Sensor 45
3.10 ‘Static’ and ‘Dynamic’ Characteristics of a Sensor 46
3.11 Frequency Response Characteristics of a Sensor 46
3.12 Impulse Response Characteristics of a Sensor 57
4 Model Based Analysis of a Sensor’s Characteristic 61
4.1 Modeling a Sensor 61
4.2 The Laplace Transform 64
4.3 Sensor’s Performance Analysis Using Laplace Transform 66
4.4 Analysis of the Behavior of a Sensor Using Transfer Function 70
4.5 Operating Environment Based Characteristics of a Sensor 79
5 Classification of Sensors 83
5.1 Active and Passive Sensors 83
5.2 Classification Based on a Sensor’s Parameter(s) 84
6 Exercises 85
2 Advanced Interfacing Techniques for the Capacitive Sensors 87
Abstract 87
1 Introduction 87
2 Capacitive Sensors for Sensing Applications 88
2.1 Parallel Plate Capacitive Sensor 88
2.2 Cylindrical Coaxial Capacitive Sensor 92
2.3 Cylindrical Cross-Capacitor 93
3 Precautions Necessary for the Use of the Capacitive Sensors 95
3.1 Shielding of the Capacitive Sensor 95
3.2 Guarding of the Capacitor Electrodes 95
3.3 Shielded Cable and the Cable Length 96
4 Lossy Capacitive Sensor 97
5 Advancement in the Design of Electronics Interface for the Capacitive Sensors 99
5.1 Introduction 99
5.2 Interface Electronics Circuit for the Capacitive Sensors 101
5.3 Oscillator Based Transformer Ratio Arm Bridge for Interfacing the Capacitive Sensor 105
5.3.1 Working of the Interface Electronic 105
5.3.2 Capacitance to Frequency Converter 107
5.3.3 Hardware Realization of the Circuit and Determination of the Response Characteristics of the Humidity Sensor 107
5.4 A Microcontroller Compatible Oscillator Based Active Bridge Circuit for Interfacing Capacitive Sensors 108
5.4.1 Working of the Circuit 108
5.4.2 Experimental Verification of the Interface Circuit 110
5.5 An Impedance Measurement Technique for Wide-Range Lossy Capacitive Sensors 112
5.5.1 Working of the Interface 112
5.5.2 An Autobalance Active Bridge 114
5.5.3 Experimental Results of the First Electronic Circuit 115
5.5.4 Experimental Results of the Autobalancing Bridge 116
5.6 Current Mode Oscillator Circuit for the Grounded Capacitive Sensors 117
5.6.1 Current Conveyer Based Oscillator 117
5.6.2 Experimental Verification of the Interface Circuit 119
6 Conclusions 121
References 121
3 A Simple Embedded Sensor: Excitation and Interfacing 124
Abstract 124
1 Introduction 124
2 Type of Sensors 125
2.1 Resistive Sensors 125
2.2 Capacitive Sensors 126
2.3 Inductive Sensors 127
3 Types of Resistive Sensors 127
3.1 Potentiometric Sensors 127
3.2 Thermistors 128
3.3 Light-Dependent Resistors 128
3.4 Piezo-Resistive Sensors 129
3.5 Resistive Level Sensor 129
3.6 Strain Gages 130
3.7 Limitations of Resistive Sensors and Need of Capacitive/Inductive Sensors 130
4 AC Excitation of Capacitive/Inductive Sensors 131
4.1 Electrochemical Impedance Spectroscopy 132
4.2 AC Bridges 132
4.3 Lissajous Curve 133
4.4 Fast Fourier Transforms 133
4.5 Phase Sensitive Detections 134
4.6 Frequency Response Analysis 134
5 Simple Embedded Processor Based Excitation System 135
5.1 Sensing System 135
5.2 Interfacing to Microcontroller 135
5.3 Power Supply Circuits 136
5.4 Generating an AC Signal 138
5.5 Measurement of the Sensing Voltage 142
5.6 Measurement of the Sensor Impedance 144
6 Result and Discussion 147
7 Improvement 150
References 150
4 Advanced Techniques for Directly Interfacing Resistive Sensors to Digital Systems 152
Abstract 152
1 Introduction 153
2 Operating Principle 154
3 Interfacing Resistive Sensors to Microcontrollers 156
3.1 Sensor 157
3.2 Microcontroller 158
3.3 Interface Circuits 160
3.4 Uncertainty Sources 162
3.5 Applications 164
4 Interfacing Resistive Sensor Arrays to FPGAs 165
4.1 Array Sensor 165
4.2 FPGA 166
4.3 Interface Circuits 167
4.4 Uncertainty Sources 170
4.5 Applications 175
5 Conclusions 175
Acknowledgements 176
References 176
Interfaces for Autarkic Wireless Sensors and Actuators in the Internet of Things 179
1 Introduction 179
2 Energy Management of Wireless Sensors 182
2.1 Energy Efficient Acquisition: Trading Energy Versus Accuracy 184
2.2 Energy Efficient Data Transmission: Trading Energy Versus Accuracy 185
3 Requirements on Protocols and Standards with Respect to Autarkic Wireless Sensors 187
4 Overview of Current IoT Approaches 187
4.1 Infrastructure Internet 187
4.2 Data Protocols 189
4.3 Semantics 190
4.4 Power Efficient Lower Layer Wireless Sensor Protocols 191
4.5 Security 192
5 Using ISO/IEC/IEEE 21450-2010 with Autarkic Wireless Sensors 192
6 ISO/IEC/IEEE 21450-2010 HTTP API 194
7 TEDS Structure and Energy Related Extensions 196
8 Steps for Using an Autarkic Wireless Sensors Example with IEEE 21450-2010 HTTP API 198
9 Summary 199
References 200
Lock-In Amplifier Architectures for Sub-ppm Resolution Measurements 202
1 Introduction 202
2 Lock-In Amplifier Working Principle 203
2.1 Digital Lock-In Amplifiers 206
3 Resolution Limit of Digital Lock-In Amplifiers 207
3.1 Lock-In Amplifiers Noise Experimental Characterization 208
3.2 Flicker Noise Sources Identification 209
4 Differential Measurements 211
5 Switched Ratiometric LIA Architectures 213
5.1 Digital Switched Ratiometric LIA with a Single ADC 213
5.2 Digital Switched Ratiometric LIA Based on Two ADCs 215
5.3 Theoretical Analysis 215
6 Enhanced-LIA Board Realization 220
6.1 Analog Architecture Design Details 220
6.2 Digital Architecture Additional Modules 222
7 Results 222
7.1 Assessment of the Resolution Capability of ELIA 223
7.2 Independence from Signal Phase and Amplitude 224
7.3 Resolution and Switching Frequency 225
8 Conclusions 226
References 227
7 Biomedical Sensors and Their Interfacing 229
Abstract 229
1 Introduction 229
2 Basic Aspects of Biomedical Data Acquisition Systems 230
3 Cardiovascular and Respiratory Signals: Origin and Basic Principle 232
3.1 Electrocardiogram Signal 232
3.2 Peripheral Pulse Signal 233
3.3 Respiration Signal 234
3.4 Blood Pressure Signal 236
4 Sensor Configurations and Interfacing of Cardiovascular and Respiratory Signals 237
4.1 Electrocardiogram Signal 237
4.1.1 Electrodes 238
4.1.2 Isolation Circuits 239
4.1.3 Filtering Circuits 240
4.1.4 Instrumentation Amplifier (INA) 241
4.2 Peripheral Pulse Signal (Photoplethysmogram) 243
4.3 Respiration Signal 244
4.3.1 Differential Pressure (DP) Respiration Sensors 245
4.3.2 Thermal Convection Type Respiration Sensors 246
4.3.3 Microwave Doppler Radar (MDR) Type Respiration Sensors 247
4.3.4 Ultrasonic Respiration Meters 248
4.3.5 Respiratory Inductive Plethysmography (RIP) Sensors 248
4.4 Blood Pressure Signal 249
4.4.1 Capacitive Blood Pressure Sensors 249
4.4.2 Piezoresistive Blood Pressure Sensors 250
4.4.3 Optical Blood Pressure Sensors 250
4.4.4 Oscillometric Blood Pressure Sensor 252
5 Wireless Biomedical Instrumentation 253
6 Trends in Biomedical Sensor Technology 254
6.1 Use of Wearable Integrated Biomedical Sensors 254
6.2 Context Aware Smart Biomedical Sensors 255
Acknowledgements 255
References 256
8 Interfacing and Pre-processing Techniques with Olfactory and Taste Sensors 259
Abstract 259
1 Electronic Nose and Tongue 260
1.1 Electronic Nose 260
1.2 Electronic Tongue 261
2 Sensors/Transducers for Electronic Nose and Tongue 261
2.1 Electronic Nose Sensors 262
2.1.1 MOS Sensor 262
2.1.2 Organic Conducting Polymer 263
2.1.3 Chemocapacitors 264
2.1.4 Potentiometric Odour Sensors 264
2.1.5 Thermal (Calorimetric) Sensors 264
2.1.6 Gravimetric Odour Sensors 265
2.1.7 Optical Odour Sensors 267
2.1.8 Fluorescent Odour Sensors 268
2.1.9 Amperometric Sensors 268
2.2 Electronic Tongue Sensors 269
2.2.1 Potentiometric Sensors 269
2.2.2 Voltammetric Sensors 270
2.2.3 Impedance Spectroscopy based Sensors 271
3 Signal Conditioning and Interfacing Circuits 272
4 Signal Preprocessing 274
5 Conclusion 275
References 275
9 Harnessing Vision and Touch for Compliant Robotic Interaction with Soft or Rigid Objects 278
Abstract 278
1 Introduction 278
2 Challenges of Robotic Interaction with Soft or Rigid Objects 280
3 Related Work on Robotic Interaction with Rigid or Soft Objects 282
4 Vision and Touch Sensing Systems for Soft Object Interaction 283
4.1 Data Acquisition 284
4.1.1 Sensor Type and Placement 284
4.1.2 Calibration 285
4.1.3 Data Acquisition Schemes 286
4.1.4 Data Cleaning and Synchronization 288
4.2 Object Modelling and Simulation 289
4.2.1 Object Position Recuperation and Segmentation 289
4.2.2 Monitoring/Tracking the Object 290
4.2.3 Object Material Characterization 291
4.2.4 Data Fusion and Deformation Prediction for Multisensory Vision and Tactile Models 292
4.2.5 3D Model Quality Assessment 294
4.3 Control Schemes for Object Interaction 295
5 Conclusion 296
Acknowledgements 296
References 297
10 IEEE1451 Smart Sensors Architectures for Vital Signs and Motor Activity Monitoring 300
Abstract 300
1 Introduction 300
2 IEEE 1451.4 Hardware Implementation 302
2.1 The Smart Gateway 303
2.2 IEEE 1451.4 Sensor Interface Module (SIM) 304
2.3 Sensor Interface Module Connection Board 307
2.4 Communication and Data Logging 308
2.5 Prototype Tests 310
3 Service eXtensions for Instrumentation 311
3.1 Communication Services 311
3.2 Control Stations 313
3.3 Engineering Stations 313
4 SXI Support for Smart Wheelchair 315
4.1 Vital Signs Measurement Channels 316
4.2 Acceleration and Force Measurement Channels 317
4.3 Data Acquisition 317
4.4 Data Processing 318
4.5 Data Monitoring 319
5 System Tests 319
5.1 Heart Rate Estimation 319
5.2 Motion Activity 320
6 Conclusion 321
References 322