Introduction to Engineering Experimentation Upplaga 3

Previous Edition TOC CHAPTER 1 Introduction 1 1.1 Applications of Engineering Experimentation and Measurement 1 1.1.1 Measurement in Engineering Experimentation 1 1.1.2 Measurement in Operational Systems 3 1.2 Objective and Overview 3 1.3 Dimensions and Units 3 1.4 Closure 5 CHAPTER 2 General Characteristics of Measurement Systems 6 2.1 Generalized Measurement System 6 2.2 Validity of Measurement 7 2.2.1 Measurement Error and Related Definitions 8 2.2.2 Calibration of Measurement Systems 15 2.3 Dynamic Measurements 23 2.4 Closure 27 References 27 Problems 28 CHAPTER 3 Measurement Systems with Electrical Signals 34 3.1 Electrical Signal Measurement Systems 34 3.2 Signal Conditioners 35 3.2.1 General Characteristics of Signal Amplification 36 3.2.2 Amplifiers Using Operational Amplifiers 42 3.2.3 Signal Attenuation 48 3.2.4 General Aspects of Signal Filtering 50 3.2.5 Butterworth Filters Using Operational Amplifiers 53 3.2.6 Circuits for Integration, Differentiation, and Comparison 57 3.3 Indicating and Recording Devices 58 3.3.1 Digital Voltmeters and Multimeters 58 3.3.2 Oscilloscopes 59 3.3.3 Strip-Chart Recorders 61 3.3.4 Data Acquisition Systems 62 3.4 Electrical Transmission of Signals Between Components 63 3.4.1 Low-Level Analog Voltage Signal Transmission 63 3.4.2 High-Level Analog Voltage Signal Transmission 65 3.4.3 Current-Loop Analog Signal Transmission 66 3.4.4 Digital Signal Transmission 66 References 67 Problems 68 CHAPTER 4 Computerized Data-Acquisition Systems 70 4.1 Introduction 70 4.2 Computer Systems 71 4.2.1 Computer Systems for Data Acquisition 71 4.2.2 Components of Computer Systems 72 4.2.3 Representing Numbers in Computer Systems 74 4.3 Data-Acquisition Components 77 4.3.1 Multiplexers 77 4.3.2 Basics of Analog-to-Digital Converters 78 4.3.3 Practical Analog-to-Digital Converters 85 4.3.4 Digital-to-Analog Converters 88 4.3.5 Simultaneous Sample-and-Hold Subsystems 89 4.4 Configurations of Data-Acquisition Systems 90 4.5 Software for Data-Acquisition Systems 92 4.5.1 Commercial Software Packages 92 References 92 Problems 93 CHAPTER 5 Discrete Sampling and Analysis of Time-Varying Signals 95 5.1 Sampling-Rate Theorem 95 5.2 Spectral Analysis of Time-Varying Signals 100 5.3 Spectral Analysis Using the Fourier Transform 105 5.4 Selecting the Sampling Rate and Filtering 110 5.4.1 Selecting the Sampling Rate 110 5.4.2 Use of Filtering to Limit Sampling Rate 111 References 115 Problems 115 CHAPTER 6 Statistical Analysis of Experimental Data 118 6.1 Introduction 118 6.2 General Concepts and Definitions 120 6.2.1 Definitions 120 6.2.2 Measures of Central Tendency 122 6.2.3 Measures of Dispersion 123 6.3 Probability 124 6.3.1 Probability Distribution Functions 125 6.3.2 Some Probability Distribution Functions with Engineering Applications 129 6.4 Parameter Estimation 139 6.4.1 Interval Estimation of the Population Mean 140 6.4.2 Interval Estimation of the Population Variance 146 6.5 Criterion for Rejecting Questionable Data Points 149 6.6 Correlation of Experimental Data 151 6.6.1 Correlation Coefficient 151 6.6.2 Least-Squares Linear Fit 155 6.6.3 Outliers in x—y Data Sets 159 6.6.4 Linear Regression Using Data Transformation 163 6.6.5 Multiple and Polynomial Regression 164 6.7 Linear Functions of Random Variables 168 6.8 Applying Computer Software for Statistical Analysis of Experimental Data 169 References 169 Problems 170 CHAPTER 7 Experimental Uncertainty Analysis 180 7.1 Introduction 180 7.2 Propagation of Uncertainties–General Considerations 180 7.3 Consideration of Systematic and Random Components of Uncertainty 184 7.4 Sources of Elemental Error 190 7.5 Uncertainty of the Final Results for Multiple-Measurement Experiments 195 7.6 Uncertainty of the Final Result for Single-Measurement Experiments 199 7.7 Step-by-Step Procedure for Uncertainty Analysis 202 7.8 Interpreting Manufacturers’ Uncertainty Data 203 7.9 Applying Uncertainty Analysis in Digital Data-Acquisition Systems 204 7.10 Additional Considerations for Single-Measurement Experiments 208 7.11 Closure 210 References 211 Problems 211 CHAPTER 8 Measurement of Solid-Mechanical Quantities 222 8.1 Measuring Strain 222 8.1.1 Electrical Resistance Strain Gage 222 8.1.2 Strain Gage Signal Conditioning 227 8.2 Measuring Displacement 232 8.2.1 Potentiometer 232 8.2.2 Linear and Rotary Variable Differential Transformers 233 8.2.3 Capacitive Displacement Sensor 237 8.2.4 Digital Encoders 239 8.3 Measuring Linear Velocity 239 8.3.1 Linear Velocity Transducer 239 8.3.2 Doppler Radar Velocity Measurement 240 8.3.3 Velocity Determination Using Displacement and Acceleration Sensors 241 8.4 Measuring Angular Velocity 242 8.4.1 Electric Generator Tachometers 242 8.4.2 Magnetic Pickup 243 8.4.3 Stroboscopic Tachometer 244 8.4.4 Photoelectric Tachometer 245 8.5 Measuring Acceleration and Vibration 245 8.5.1 Piezoelectric Accelerometers 245 8.5.2 Strain-Gage Accelerometers 248 8.5.3 Servo Accelerometer 249 8.5.4 Vibrometer 249 8.6 Measuring Force 250 8.6.1 Load Cells 250 8.6.2 Proving Rings 252 8.7 Measuring Rotating Shaft Torque 253 References 255 Problems 256 CHAPTER 9 Measuring Pressure, Temperature, and Humidity 261 9.1 Measuring Pressure 261 9.1.1 Traditional Pressure-Measuring Devices 261 9.1.2 Pressure Transducers 268 9.1.3 Measuring a Vacuum 270 9.2 Measuring Temperature 274 9.2.1 Thermocouples 274 9.2.2 Resistance-Temperature Detectors 281 9.2.3 Thermistor and Integrated-Circuit Temperature Sensors 285 9.2.4 Mechanical Temperature-Sensing Devices 286 9.2.5 Pyrometers and Infrared Thermometers 289 9.2.6 Common Temperature-Measurement Errors 293 9.3 Measuring Humidity 298 9.3.1 Hygrometric Devices 299 9.3.2 Dew-Point Devices 299 9.3.3 Psychrometric Devices 299 WheeFMv3.qxd 4/18/03 12:47 PM Page vi Contents vii 9.4 Fiber-Optic Devices 301 9.4.1 Optical Fiber 301 9.4.2 General Characteristics of Fiber-Optic Sensors 303 9.4.3 Fiber-Optic Displacement Sensors 304 9.4.4 Fiber-Optic Temperature Sensors 305 9.4.5 Fiber Optic Pressure Sensors 307 9.4.6 Other Fiber-Optic Sensors 307 References 308 Problems 309 CHAPTER 10 Measuring Fluid Flow Rate, Fluid Velocity, Fluid Level, and Combustion Pollutants 313 10.1 Systems for Measuring Fluid Flow Rate 313 10.1.1 Pressure Differential Devices 313 10.1.2 Variable-Area Flowmeters 329 10.1.3 Turbine Flowmeters 332 10.1.4 Mass Flowmeters 333 10.1.5 Positive-Displacement Flowmeters 336 10.1.6 Other Methods of Flow Measurement 336 10.1.7 Calibrating Flowmeters 340 10.2 Systems for Measuring Fluid Velocity 341 10.2.1 Pitot-Static Probe 341 10.2.2 Hot-Wire and Hot-Film Anemometers 343 10.2.3 Fluid Velocity Measurement Using the Laser-Doppler Effect 345 10.3 Measuring Fluid Level 347 10.3.1 Buoyancy Devices 348 10.3.2 Differential-Pressure Devices 349 10.3.3 Capacitance Devices 350 10.3.4 Conductance Devices 351 10.3.5 Ultrasonic Devices 351 10.3.6 Weight Methods 352 10.4 Measuring Air Pollution Species 352 10.4.1 Nondispersive Infrared Detectors 353 10.4.2 Chemiluminescent Analyzers 354 10.4.3 Flame Ionization Detectors 355 10.4.4 Other Gas-Analysis Devices 356 10.4.5 General Considerations about Sampling and Measuring Pollutant Gases 357 References 358 Problems 359 CHAPTER 11 Dynamic Behavior of Measurement Systems 363 11.1 Order of a Dynamic Measurement System 363 11.2 Zero-Order Measurement Systems 364 11.3 First-Order Measurement Systems 364 11.3.1 Basic Equations 365 11.3.2 Step Input 365 11.3.3 Ramp Input 366 11.3.4 Sinusoidal Input 368 11.3.5 Thermocouple as a First-Order System 368 11.4 Second-Order Measurement Systems 373 11.4.1 Basic Equations 373 11.4.2 Step Input 374 11.4.3 Sinusoidal Input 376 11.4.4 Force Transducer (Load Cell) as a Second-Order System 377 11.4.5 Pressure-Measurement Devices as Second-Order Systems 380 11.4.6 Second-Order Systems for Acceleration and Vibration 388 11.5 Closure 393 References 394 Problems 394 CHAPTER 12 Guidelines for Planning and Documenting Experiments 397 12.1 Overview of an Experimental Program 397 12.1.1 Problem Definition 397 12.1.2 Experiment Design 398 12.1.3 Experiment Construction and Development 398 12.1.4 Data Gathering 399 12.1.5 Data Analysis 399 12.1.6 Interpreting Data and Reporting 399 12.2 Common Activities in Experimental Projects 399 12.2.1 Dimensional Analysis and Determining the Test Rig Scale 399 12.2.2 Uncertainty Analysis 403 12.2.3 Shakedown Tests 403 12.2.4 Test Matrix and Test Sequence 404 12.2.5 Scheduling and Cost Estimation 408 12.2.6 Design Review 412 12.2.7 Documenting Experimental Activities 413 12.3 Closure 421 References 421 Answers to Selected Problems 422 APPENDIX A Computational Methods for Chapter 5 425 APPENDIX B Selected Properties of Substances 429 Glossary 434 Index