Instrumentation for Engineering Measurements

List of Symbols Chapter 1 Applications of Electronic Instrument Systems 1.1 Introduction 1.2 The Electronic Instrument System 1.3 Engineering Analysis 1.4 Process Control 1.4.1 Process Control Devices 1.5 Experimental Error 1.5.1 Accumulation of Accepted Error 1.5.2 Improper Functioning of Instruments 1.5.3 Effect of the Transducer on the Process 1.5.4 Dual Sensitivity Errors 1.5.5 Other Sources of Error 1.6 Minimizing Experimental Error 1.7 Summary References Exercises Chapter 2 Analysis of Circuits 2.1 Introduction and Definitions 2.2 Basic Electrical Components 2.3 Kirchhoff's Circuit Laws 2.4 Diodes, Transistors, and Gates 2.4.1 Diodes 2.4.2 Transistors 2.4.3 Gates 2.5 DC Circuits 2.6 Periodic Functions 2.7 AC Circuits 2.7.1 Impedance 2.8 Frequency Response Function 2.9 Summary References Exercises Chapter 3 Analog Recording Instruments 3.1 Introduction 3.2 General Characteristics of Recording Instruments 3.3 Voltmeters for Steady-State Measurements 3.3.1 D'arsonval Galvanometer 3.3.2 Ammeter 3.3.3 DC Voltmeters 3.3.4 Voltmeter Loading Errors 3.3.5 Amplified Voltmeters 3.3.6 Potentiometric Voltmeters 3.4 Voltmeters for Slowly Varying Signals 3.4.1 Strip-Chart Recorders 3.4.2 X-Y Recorders 3.5 Voltmeters for Rapidly Varying Signals 3.5.1 Oscillograph Recorders 3.5.2 Transient Response of Galvanometers 3.5.3 Periodic Signal Response of Galvanometers 3.5.4 Oscilloscopes 3.5.5 Magnetic Tape Recorders 3.6 Summary References Exercises Chapter 4 Digital Recording Systems 4.1 Introduction 4.2 Digital Codes 4.3 Conversion Processes 4.4 Digital-to-Analog Converters 4.5 Analog-to-Digital Converters 4.5.1 Successive-Approximation Method 4.5.2 Intergration Method 4.5.3 Parallel or Flash Method 4.6 Data Distribution 4.6.1 Bus Structures 4.7 Interfaces 4.8 Digital Voltmeters 4.9 Data-Logging Systems 4.10 Data-Acquisition Systems 4.11 PC-Based Data-Acquisition Systems 4.12 Digital Oscilloscopes 4.13 Waveform Recorders 4.14 Aliasing 4.14.1 Antialiasing Filters 4.15 Summary References Exercises Chapter 5 Sensors for Transducers 5.1 Introduction 5.2 Potentiometers 5.3 Differential Transformers 5.4 Resistance Strain Gages 5.5 Capacitance Sensors 5.6 Eddy-Current Sensors 5.7 Piezoelectric Sensors 5.8 Piezoresistive Sensors 5.9 Photoelectric Sensors 5.9.1 Vacuum-Tube Detectors 5.9.2 Photoconductive Cells 5.9.3 Semiconductor Photodiodes 5.10 Resistance Temperature Detectors 5.11 Thermistors 5.12 Thermocouples 5.13 Crystal Oscillators 5.14 Summary References Exercises Chapter 6 Signal Conditioning Circuits 6.1 Introduction 6.2 Power Supplies 6.2.1 Battery Supplies 6.2.2 Line Voltage Supplies 6.3 Potentiometer Circuit (Constant Voltage) 6.4 Potentiometer Circuit (Constant Current) 6.5 Wheatstone Bridge (Constant Voltage) 6.6 Wheatstone Bridge (Constant Current) 6.7 Amplifiers 6.8 Operational Amplifiers 6.8.1 Inverting Amplifier 6.8.2 Differential Amplifier 6.8.3 Voltage Follower 6.8.4 Summing Amplifier 6.8.5 Integrating Amplifier 6.8.6 Differentiating Amplifier 6.9 Filters 6.9.1 High-Pass RC Filter 6.9.2 Low-Pass RC Filter 6.9.3 Active Filter 6.10 Amplitude Modulation and Demodulation 6.11 Time-Measuring Circuits 6.11.1 Binary Counting Unit 6.11.2 Gates in Counter Applications 6.11.3 Triggers 6.11.4 Counting Instruments 6.12 Summary References Exercises Chapter 7 Resistance-Type Strain Gages 7.1 Introduction 7.2 Etched-Foil Strain Gages 7.3 Strain-Gage Installation 7.4 Wheatstone Bridge Signal Conditioning 7.5 Recording Instruments for Strain Gages 7.5.1 Direct-Reading Strain Indicator 7.5.2 Null-Balance Bridges 7.5.3 Strain-Gage Signal Conditioners 7.5.4 Wheatstone Bridge and Oscilloscope 7.5.5 Wheatstone Bridge and Oscillograph 7.6 Calibration Methods 7.7 Effects of Lead Wires, Switches, and Slip Rings 7.7.1 Lead Wires 7.7.2 Switches 7.7.3 Slip Rings 7.8 Electrical Noise 7.9 Temperature-Compensated Gages 7.10 Alloy Sensitivity, Gage Factor, and Cross-Sensitivity Factors 7.11 Data-Reduction Methods 7.11.1 The Uniaxial State of Stress 7.11.2 The Biaxial State of Stress 7.11.3 The General State of Stress 7.12 High-Temperature Strain Measurements 7.13 Summary References Exercises Chapter 8 Force, Torque, and Pressure Measurements 8.1 Introduction 8.2 Force Measurements (Load Cells) 8.2.1 Link-Type Load Cell 8.2.2 Beam-Type Load Cell 8.2.3 Ring-Type Load Cell 8.2.4 Shear-Web-Type Load Cell 8.3 Torque Measurement (Torque Cells) 8.3.1 Torque Cells - Design Concepts 8.3.2 Torque Cells - Data Transmission 8.4 Combined Measurements of Force and Moments or Torques 8.4.1 Force-Moment Measurements 8.4.2 Force-Torque Measurements 8.5 Pressure Measurements (Pressure Transducers) 8.5.1 Displacement-Type Pressure Transducer 8.5.2 Diaphragm-Type Pressure Transducer 8.5.3 Piezoelectric-Type Pressure Transducer 8.6 Minimizing Errors in Transducers 8.6.1 Dual Sensitivity 8.6.2 Zero Shift with Temperature Change 8.6.3 Bridge Balance 8.6.4 Span Adjust 8.6.5 Span Change with Temperature 8.7 Frequency Response of Transducers 8.7.1 Response of a Force Transducer to a Terminated Ramp Function 8.7.2 Response of a Force Transducer to a Sinusoidal Forcing Function 8.8 Calibration of Transducers 8.9 Summary References Exercises Chapter 9 Displacement, Velocity, and Acceleration Measurements 9.1 Introduction 9.2 The Seismic Transducer Model 9.3 Dynamic Response of the Seismic Model 9.3.1 Sinusoidal Excitation 9.3.2 Transient Excitations 9.4 Seismic Motion Transducers 9.4.1 Seismic Displacement Transducers 9.4.2 Seismic Velocity Transducers 9.4.3 Seismic Acceleration Transducers 9.5 Piezoelectric Force Transducers 9.6 Piezoelectric Sensor Circuits 9.6.1 Charge Sensitivity Model 9.6.2 Voltage-Follower Circuit 9.6.3 Charge-Amplifier Circuit 9.6.4 Built-in Voltage Followers 9.7 Response of Piezoelectric Circuits to Transient Signals 9.8 Accelerometer Calibration 9.9 Dynamic Calibration of Force Transducers 9.9.1 Force Transducer Calibration by Impact 9.10 Overall System Calibration 9.11 Sources of Error with Piezoelectric Transducers 9.12 Displacement Measurements in a Fixed Reference Frame 9.12.1 Displacement Measurements with Resistance Potentiometers 9.12.2 Displacement Measurements with Multiple-Resistor Devices 9.12.3 Photoelectric Displacement Transducers 9.13 Optical Displacement Measurements 9.13.1 Optical Tracker System 9.13.2 Video Camera Motion Analysis 9.14 Velocity Measurements 9.14.1 Linear-Velocity Measurements 9.14.2 Angular-Velocity Measurements 9.14.3 Laser-Doppler System 9.15 Summary References Exercises Chapter 10 Analysis of Vibrating Systems 10.1 Introduction 10.1.1 Temporal Mean 10.1.2 Temporal Mean Square and Root Mean Square 10.2 Sinusoidal Signal Analysis 10.3 Characteristics of Signals 10.3.1 Periodic Signals 10.3.2 Transient Signals 10.3.3 Random Signals 10.4 Lumped Mass-Spring Vibration Models 10.4.1 Undamped Natural Frequency and Mode Shape 10.4.2 Forced Vibration Response (Direct Solution) 10.4.3 Forced Vibration Response (Modal Solution) 10.5 Continuous Vibration Models 10.5.1 Fundamental Equation of Motion 10.5.2 Steady-State Modal Solution 10.6 The Linear Input-Output Model 10.6.1 Impulse Response 10.6.2 Random Input-Output Relationships 10.7 Basics of a Digital Frequency Analyzer 10.7.1 Time Sampling Process 10.7.2 Convolution 10.7.3 Filter Leakage 10.7.4 Block Diagram 10.8 Using a Digital Frequency Analyzer 10.8.1 Relationships for Frequency Analyzers 10.8.2 Filter Characteristics 10.8.3 Four Common Window Functions 10.8.4 Uncertainty in the Magnitude of Spectral Lines 10.8.5 Summary of Window Use 10.9 Accelerometer Cross-Axis Sensitivity 10.9.1 Single Accelerometer Cross-Axis Coupling Model 10.9.2 Triaxial Accelerometer Model 10.9.3 Correcting Acceleration Voltage Readings 10.9.4 Application to Modal Analysis Signals 10.9.5 Cross-Axis Resonance 10.10 Force Transducer-Structure Interaction 10.10.1 General Two-Degree-of-Freedom Force Transducer Model 10.11 Summary References Exercises Chapter 11 Temperature Measurements 11.1 Introduction 11.2 Expansion Methods for Measuring Temperature 11.3 Resistance Thermometers 11.3.1 Resistance Temperature Detectors (RTDS) 11.3.2 RTDS and the Wheatstone Bridge 11.3.3 Thermistors 11.4 Thermocouples 11.4.1 Principles of Thermocouple Behavior 11.4.2 Thermoelectric Materials 11.4.3 Reference Junction Temperature 11.4.4 Fabrication and Installation Procedures 11.4.5 Recording Instruments for Thermocouples 11.4.6 Noise Suppression in Thermocouple Circuits 11.5 Integrated-Circuit Temperature Sensors 11.6 Dynamic Response of Temperature Sensors 11.7 Sources of Error in Temperature Measurements 11.8 Calibration Methods 11.9 Radiation Methods (Pyrometry) 11.9.1 Principles of Radiation 11.9.2 The Optical Pyrometer 11.9.3 Infrared Pyrometers 11.9.4 Photon Detector Temperature Instruments 11.10 Summary References Exercises Chapter 12 Fluid Flow Measurements 12.1 Introduction 12.2 Flow Velocity (Insertion-Type Transducers) 12.2.1 Pitot Tube (Incompressible Flow) 12.2.2 Pitot Tube (Compressible Flow) 12.2.3 Hot-Wire and Hot-Film Anemometers 12.2.4 Drag-Force Velocity Transducers 12.2.5 Current Meters 12.2.6 Turbine Flow Meters 12.2.7 Vortex-Shedding Transducers 12.3 Flow Rates in Closed Systems by Pressure-Variation Measurements 12.3.1 Venturi Meter 12.3.2 Flow Nozzle 12.3.3 Orifice Meter 12.3.4 Elbow Meter 12.4 Flow Rates in Partially Closed Systems 12.5 Flow Rates in Open Channels from Pressure Measurements 12.5.1 Sluice Gate 12.5.2 Weirs 12.6 Compressible Flow Effects in Closed Systems 12.7 Other Flow-Measurement Methods for Closed Systems 12.7.1 Capillary Flow Meter 12.7.2 Positive-Displacement Flow Meters 12.7.3 Hot-Film Mass Flow Transducers 12.7.4 Laser Velocimetry Systems 12.8 Summary References Exercises Chapter 13 Statistical Methods 13.1 Introduction 13.2 Characterizing Statistical Distributions 13.2.1 Graphic Representations of the Distribution 13.2.2 Measures of Central Tendency 13.2.3 Measures of Dispersion 13.3 Statistical Distribution Functions 13.3.1 Gaussian Distribution 13.3.2 Weibull Distribution 13.4 Confidence Intervals for Predictions 13.5 Comparision of Means 13.6 Statistical Conditioning of Data 13.7 Regression Analysis 13.7.1 Linear Regression Analysis 13.7.2 Multivariate Regression 13.8 Chi-Square Testing 13.9 Error Accumulation and Propagation 13.10 Summary References Exercises Appendix A Appendix B Author Index Subject Index