Experimentation. Third Edition. Wheeler. Ahmad R. Ganji. School of Engineering. With Third Edition contributions by. V. V. Krishnan. Brian S.

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1 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

2 Contents Preface 9 CHAPTER 1 Introduction Applications of Engineering Experimentation and Measurement Measurement in Engineering Experimentation Measurement in Operational Systems Objective and Overview Dimensions and Units Closure 15 Problems 15 CHAPTER 2 General Characteristics of Measurement Systems Generalized Measurement System Validity of Measurement Measurement Error and Related Definitions Calibration of Measurement Systems Dynamic Measurements Closure 38 References 38 Problems 39 CHAPTER 3 Measurement Systems with Electrical Signals Electrical Signal Measurement Systems Signal Conditioners General Characteristics of Signal Amplification Amplifiers Using Operational Amplifiers Signal Attenuation General Aspects of Signal Filtering Butterworth Filters Using Operational Amplifiers Circuits for Integration, Differentiation, and Comparison Indicating and Recording Devices Digital Voltmeters and Multimeters Oscilloscopes Strip-Chart Recorders Data Acquisition Systems Electrical Transmission of Signals Between Components Low-Level Analog Voltage Signal Transmission High-Level Analog Voltage Signal Transmission Current-Loop Analog Signal Transmission Digital Signal Transmission 78 References 78 Problems 78 3

3 4 Contents CHAPTER 4 Computerized Data-Acquisition Systems Introduction Computer Systems Computer Systems for Data Acquisition Components of Computer Systems Representing Numbers in Computer Systems Data-Acquisition Components Multiplexers Basics of Analog-to-Digital Converters Practical Analog-to-Digital Converters Digital-to-Analog Converters Simultaneous Sample-and-Hold Subsystems Configurations of Data-Acquisition Systems Internal Single Board Plug-in Systems External Systems Digital Connectivity Virtual Instruments Digital Storage Oscilloscopes Data Loggers Software for Data-Acquisition Systems Commercial Software Packages 108 References 108 Problems 109 CHAPTER 5 Discrete Sampling and Analysis of Time-Varying Signals Sampling-Rate Theorem Spectral Analysis of Time-Varying Signals Spectral Analysis Using the Fourier Transform Selecting the Sampling Rate and Filtering Selecting the Sampling Rate Use of Filtering to Limit Sampling Rate 131 References 134 Problems 135 CHAPTER 6 Statistical Analysis of Experimental Data Introduction General Concepts and Definitions Definitions Measures of Central Tendency Measures of Dispersion Probability Probability Distribution Functions Some Probability Distribution Functions with Engineering Applications Parameter Estimation Interval Estimation of the Population Mean Interval Estimation of the Population Variance 170

4 Contents Criterion for Rejecting Questionable Data Points Correlation of Experimental Data Correlation Coefficient Least-Squares Linear Fit Outliers in x-y Data Sets Linear Regression Using Data Transformation Multiple and Polynomial Regression Linear Functions of Random Variables Applying Computer Software for Statistical Analysis of Experimental Data 195 References 195 Problems 196 CHAPTER 7 Experimental Uncertainty Analysis Introduction Propagation of Uncertainties General Considerations Consideration of Systematic and Random Components of Uncertainty Sources of Elemental Error Uncertainty of the Final Results for Multiple-Measurement Experiments Uncertainty of the Final Result for Single-Measurement Experiments Step-by-Step Procedure for Uncertainty Analysis Interpreting Manufacturers' Uncertainty Data Applying Uncertainty Analysis in Digital Data-Acquisition Systems Additional Considerations for Single-Measurement Experiments Closure 240 References 240 Problems 240 CHAPTER 8 Measurement of Solid-Mechanical Quantities Measuring Strain Electrical Resistance Strain Gage Strain Gage Signal Conditioning Measuring Displacement Potentiometer Linear and Rotary Variable Differential Transformers Capacitive Displacement Sensor Digital Encoders Measuring Linear Velocity Linear Velocity Transducer Doppler Radar Velocity Measurement Velocity Determination Using Displacement and Acceleration Sensors 273

5 6 Contents 8.4 Measuring Angular Velocity Electric Generator Tachometers Magnetic Pickup Stroboscopic Tachometer Photoelectric Tachometer Measuring Acceleration and Vibration Piezoelectric Accelerometers Strain-Gage Accelerometers Servo Accelerometer Vibrometer Measuring Force Load Cells Proving Rings Measuring Rotating Shaft Torque 285 References 287 Problems 288 CHAPTER 9 Measuring Pressure,Temperature, and Humidity Measuring Pressure Traditional Pressure-Measuring Devices Pressure Transducers Measuring a Vacuum Measuring Temperature Thermocouples Resistance-Temperature Detectors Thermistor and Integrated-Circuit Temperature Sensors Mechanical Temperature-Sensing Devices Radiation Thermometers (Pyrometers) Common Temperature-Measurement Errors Measuring Humidity Hygrometric Devices Dew-Point Devices Psychrometric Devices Fiber-Optic Devices Optical Fiber General Characteristics of Fiber-Optic Sensors Fiber-Optic Displacement Sensors Fiber-Optic Temperature Sensors Fiber Optic Pressure Sensors Other Fiber-Optic Sensors 341 References 341 Problems 342 CHAPTER 10 Measuring Fluid Flow Rate, Fluid Velocity, Fluid Level, and Combustion Pollutants Systems for Measuring Fluid Flow Rate Pressure Differential Devices 346

6 Contents Variable-Area Flowmeters Turbine Flowmeters Mass Flowmeters Positive-Displacement Flowmeters Other Methods of Flow Measurement Calibrating Flowmeters Systems for Measuring Fluid Velocity Pitot-Static Probe Hot-Wire and Hot-Film Anemometers Fluid Velocity Measurement Using the Laser-Doppler Effect Measuring Fluid Level Buoyancy Devices Differential-Pressure Devices Capacitance Devices Conductance Devices Ultrasonic Devices Weight Methods Measuring Air Pollution Species Nondispersive Infrared Detectors Chemiluminescent Analyzers Flame Ionization Detectors Other Gas-Analysis Devices General Considerations about Sampling and Measuring Pollutant Gases 390 References 391 Problems 392 CHAPTER 11 Dynamic Behavior of Measurement Systems Order of a Dynamic Measurement System Zero-Order Measurement Systems First-Order Measurement Systems Basic Equations Step Input Ramp Input Sinusoidal Input Thermocouple as a First-Order System Second-Order Measurement Systems Basic Equations Step Input Sinusoidal Input Force Transducer (Load Cell) as a Second-Order System Pressure-Measurement Devices as Second-Order Systems Second-Order Systems for Acceleration and Vibration Closure 427 References 428 Problems 428

7 8 Contents CHAPTER 12 Guidelines for Planning and Documenting Experiments Overview of an Experimental Program Problem Definition Experiment Design Experiment Construction and Development Data Gathering Data Analysis Interpreting Data and Reporting Common Activities in Experimental Projects Dimensional Analysis and Determining the Test Rig Scale Uncertainty Analysis Shakedown Tests Test Matrix and Test Sequence Scheduling and Cost Estimation Design Review 447 Activities Documenting Experimental 12.3 Closure 456 References 456 Answers to Selected Problems 457 APPENDIX A Computational Methods for Chapter APPENDIX B Selected Properties of Substances 463 Glossary 468 Index 476

Theory and Design for Mechanical Measurements

Theory and Design for Mechanical Measurements Third Edition Richard S. Figliola Clemson University Donald E. Beasley Clemson University John Wiley & Sons, Inc. New York / Chichester / Weinheim / Brisbane