Introduction to Engineering Experimentation Third Edition Anthony J. Ahmad R. Wheeler Ganji School of Engineering San Francisco State University With Third Edition contributions by V. V. Krishnan San Francisco State University Brian S. Thurow Auburn University PEARSON Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Singapore Taipei Tokyo
Contents Preface 9 CHAPTER 1 Introduction 11 1.1 Applications of Engineering Experimentation and Measurement 11 1.1.1 Measurement in Engineering Experimentation 11 1.1.2 Measurement in Operational Systems 13 1.2 Objective and Overview 13 1.3 Dimensions and Units 13 1.4 Closure 15 Problems 15 CHAPTER 2 General Characteristics of Measurement Systems 17 2.1 Generalized Measurement System 17 2.2 Validity of Measurement 18 2.2.1 Measurement Error and Related Definitions 19 2.2.2 Calibration of Measurement Systems 26 2.3 Dynamic Measurements 34 2.4 Closure 38 References 38 Problems 39 CHAPTER 3 Measurement Systems with Electrical Signals 46 3.1 Electrical Signal Measurement Systems 46 3.2 Signal Conditioners 47 3.2.1 General Characteristics of Signal Amplification 48 3.2.2 Amplifiers Using Operational Amplifiers 54 3.2.3 Signal Attenuation 60 3.2.4 General Aspects of Signal Filtering 62 3.2.5 Butterworth Filters Using Operational Amplifiers 65 3.2.6 Circuits for Integration, Differentiation, and Comparison 69 3.3 Indicating and Recording Devices 70 3.3.1 Digital Voltmeters and Multimeters 70 3.3.2 Oscilloscopes 71 3.3.3 Strip-Chart Recorders 73 3.3.4 Data Acquisition Systems 74 3.4 Electrical Transmission of Signals Between Components 74 3.4.1 Low-Level Analog Voltage Signal Transmission 74 3.4.2 High-Level Analog Voltage Signal Transmission 77 3.4.3 Current-Loop Analog Signal Transmission 77 3.4.4 Digital Signal Transmission 78 References 78 Problems 78 3
4 Contents CHAPTER 4 Computerized Data-Acquisition Systems 81 4.1 Introduction 81 4.2 Computer Systems 82 4.2.1 Computer Systems for Data Acquisition 82 4.2.2 Components of Computer Systems 83 4.2.3 Representing Numbers in Computer Systems 85 4.3 Data-Acquisition Components 88 4.3.1 Multiplexers 88 4.3.2 Basics of Analog-to-Digital Converters 89 4.3.3 Practical Analog-to-Digital Converters 96 4.3.4 Digital-to-Analog Converters 100 4.3.5 Simultaneous Sample-and-Hold Subsystems 101 4.4 Configurations of Data-Acquisition Systems 102 4.4.1 Internal Single Board Plug-in Systems 102 4.4.2 External Systems 102 4.4.3 Digital Connectivity 103 4.4.4 Virtual Instruments 104 4.4.5 Digital Storage Oscilloscopes 105 4.4.6 Data Loggers 107 4.5 Software for Data-Acquisition Systems 107 4.5.1 Commercial Software Packages 108 References 108 Problems 109 CHAPTER 5 Discrete Sampling and Analysis of Time-Varying Signals 112 5.1 Sampling-Rate Theorem 112 5.2 Spectral Analysis of Time-Varying Signals 117 5.3 Spectral Analysis Using the Fourier Transform 122 5.4 Selecting the Sampling Rate and Filtering 129 5.4.1 Selecting the Sampling Rate 129 5.4.2 Use of Filtering to Limit Sampling Rate 131 References 134 Problems 135 CHAPTER 6 Statistical Analysis of Experimental Data 138 6.1 Introduction 138 6.2 General Concepts and Definitions 140 6.2.1 Definitions 140 6.2.2 Measures of Central Tendency 142 6.2.3 Measures of Dispersion 143 6.3 Probability 144 6.3.1 Probability Distribution Functions 145 6.3.2 Some Probability Distribution Functions with Engineering Applications 149 6.4 Parameter Estimation 161 6.4.1 Interval Estimation of the Population Mean 162 6.4.2 Interval Estimation of the Population Variance 170
Contents 5 6.5 Criterion for Rejecting Questionable Data Points 173 6.6 Correlation of Experimental Data 175 6.6.1 Correlation Coefficient 175 6.6.2 Least-Squares Linear Fit 179 6.6.3 Outliers in x-y Data Sets 185 6.6.4 Linear Regression Using Data Transformation 188 6.6.5 Multiple and Polynomial Regression 190 6.7 Linear Functions of Random Variables 194 6.8 Applying Computer Software for Statistical Analysis of Experimental Data 195 References 195 Problems 196 CHAPTER 7 Experimental Uncertainty Analysis 209 7.1 Introduction 209 7.2 Propagation of Uncertainties General Considerations 209 7.3 Consideration of Systematic and Random Components of Uncertainty 212 7.4 Sources of Elemental Error 219 7.5 Uncertainty of the Final Results for Multiple-Measurement Experiments 224 7.6 Uncertainty of the Final Result for Single-Measurement Experiments 228 7.7 Step-by-Step Procedure for Uncertainty Analysis 231 7.8 Interpreting Manufacturers' Uncertainty Data 232 7.9 Applying Uncertainty Analysis in Digital Data-Acquisition Systems 233 7.10 Additional Considerations for Single-Measurement Experiments 237 7.11 Closure 240 References 240 Problems 240 CHAPTER 8 Measurement of Solid-Mechanical Quantities 254 8.1 Measuring Strain 254 8.1.1 Electrical Resistance Strain Gage 254 8.1.2 Strain Gage Signal Conditioning 259 8.2 Measuring Displacement 264 8.2.1 Potentiometer 264 8.2.2 Linear and Rotary Variable Differential Transformers 265 8.2.3 Capacitive Displacement Sensor 269 8.2.4 Digital Encoders 271 8.3 Measuring Linear Velocity 271 8.3.1 Linear Velocity Transducer 271 8.3.2 Doppler Radar Velocity Measurement 272 8.3.3 Velocity Determination Using Displacement and Acceleration Sensors 273
6 Contents 8.4 Measuring Angular Velocity 274 8.4.1 Electric Generator Tachometers 274 8.4.2 Magnetic Pickup 275 8.4.3 Stroboscopic Tachometer 276 8.4.4 Photoelectric Tachometer 277 8.5 Measuring Acceleration and Vibration 277 8.5.1 Piezoelectric Accelerometers 277 8.5.2 Strain-Gage Accelerometers 280 8.5.3 Servo Accelerometer 281 8.5.4 Vibrometer 281 8.6 Measuring Force 282 8.6.1 Load Cells 282 8.6.2 Proving Rings 284 8.7 Measuring Rotating Shaft Torque 285 References 287 Problems 288 CHAPTER 9 Measuring Pressure,Temperature, and Humidity 294 9.1 Measuring Pressure 294 9.1.1 Traditional Pressure-Measuring Devices 294 9.1.2 Pressure Transducers 301 9.1.3 Measuring a Vacuum 303 9.2 Measuring Temperature 307 9.2.1 Thermocouples 307 9.2.2 Resistance-Temperature Detectors 314 9.2.3 Thermistor and Integrated-Circuit Temperature Sensors 318 9.2.4 Mechanical Temperature-Sensing Devices 320 9.2.5 Radiation Thermometers (Pyrometers) 322 9.2.6 Common Temperature-Measurement Errors 325 9.3 Measuring Humidity 331 9.3.1 Hygrometric Devices 331 9.3.2 Dew-Point Devices 332 9.3.3 Psychrometric Devices 332 9.4 Fiber-Optic Devices 334 9.4.1 Optical Fiber 334 9.4.2 General Characteristics of Fiber-Optic Sensors 336 9.4.3 Fiber-Optic Displacement Sensors 337 9.4.4 Fiber-Optic Temperature Sensors 338 9.4.5 Fiber Optic Pressure Sensors 340 9.4.6 Other Fiber-Optic Sensors 341 References 341 Problems 342 CHAPTER 10 Measuring Fluid Flow Rate, Fluid Velocity, Fluid Level, and Combustion Pollutants 346 10.1 Systems for Measuring Fluid Flow Rate 346 10.1.1 Pressure Differential Devices 346
Contents 7 10.1.2 Variable-Area Flowmeters 362 10.1.3 Turbine Flowmeters 365 10.1.4 Mass Flowmeters 366 10.1.5 Positive-Displacement Flowmeters 369 10.1.6 Other Methods of Flow Measurement 369 10.1.7 Calibrating Flowmeters 373 10.2 Systems for Measuring Fluid Velocity 374 10.2.1 Pitot-Static Probe 374 10.2.2 Hot-Wire and Hot-Film Anemometers 376 10.2.3 Fluid Velocity Measurement Using the Laser-Doppler Effect 378 10.3 Measuring Fluid Level 381 10.3.1 Buoyancy Devices 381 10.3.2 Differential-Pressure Devices 382 10.3.3 Capacitance Devices 383 10.3.4 Conductance Devices 384 10.3.5 Ultrasonic Devices 384 10.3.6 Weight Methods 385 10.4 Measuring Air Pollution Species 385 10.4.1 Nondispersive Infrared Detectors 386 10.4.2 Chemiluminescent Analyzers 388 10.4.3 Flame Ionization Detectors 389 10.4.4 Other Gas-Analysis Devices 390 10.4.5 General Considerations about Sampling and Measuring Pollutant Gases 390 References 391 Problems 392 CHAPTER 11 Dynamic Behavior of Measurement Systems 397 11.1 Order of a Dynamic Measurement System 397 11.2 Zero-Order Measurement Systems 398 11.3 First-Order Measurement Systems 398 11.3.1 Basic Equations 399 11.3.2 Step Input 399 11.3.3 Ramp Input 400 11.3.4 Sinusoidal Input 402 11.3.5 Thermocouple as a First-Order System 402 11.4 Second-Order Measurement Systems 407 11.4.1 Basic Equations 407 11.4.2 Step Input 408 11.4.3 Sinusoidal Input 410 11.4.4 Force Transducer (Load Cell) as a Second-Order System 411 11.4.5 Pressure-Measurement Devices as Second-Order Systems 414 11.4.6 Second-Order Systems for Acceleration and Vibration 423 11.5 Closure 427 References 428 Problems 428
8 Contents CHAPTER 12 Guidelines for Planning and Documenting Experiments 432 12.1 Overview of an Experimental Program 432 12.1.1 Problem Definition 432 12.1.2 Experiment Design 433 12.1.3 Experiment Construction and Development 433 12.1.4 Data Gathering 434 12.1.5 Data Analysis 434 12.1.6 Interpreting Data and Reporting 434 12.2 Common Activities in Experimental Projects 434 12.2.1 Dimensional Analysis and Determining the Test Rig Scale 434 12.2.2 Uncertainty Analysis 438 12.2.3 Shakedown Tests 438 12.2.4 Test Matrix and Test Sequence 439 12.2.5 Scheduling and Cost Estimation 443 12.2.6 Design Review 447 Activities 448 12.2.7 Documenting Experimental 12.3 Closure 456 References 456 Answers to Selected Problems 457 APPENDIX A Computational Methods for Chapter 5 460 APPENDIX B Selected Properties of Substances 463 Glossary 468 Index 476