Table Of ContentIntroduction to Engineering
Experimentation
Third Edition
Anthony J. Wheeler
Ahmad R. 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
Prentice Hall
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Library of Congress Cataloging-in-Publication Data
Wheeler,Anthony J.
Introduction to engineering experimentation / Anthony J.Wheeler,Ahmad R.Ganji;
with contributions by V.V.Krishnan,Brian S.Thurow.—3rd ed.
p.cm.
Includes bibliographical references and index.
ISBN 978-0-13-174276-5 (alk.paper)
1. Engineering—Experiments.2. Experimental design.I.Ganji,A.R.(Ahmad Reza) II.Title.
TA153.W47 2004
620.0078—dc22 2009045089
10 9 8 7 6 5 4 3 2 1
ISBN-13: 978-0-13-174276-5
ISBN-10: 0-13-174276-0
Contents
Preface ix
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 4
1.4 Closure 5
Problems 5
CHAPTER 2 General Characteristics of Measurement Systems 7
2.1 Generalized Measurement System 7
2.2 Validity of Measurement 8
2.2.1 Measurement Error and Related Definitions 9
2.2.2 Calibration of Measurement Systems 16
2.3 Dynamic Measurements 24
2.4 Closure 28
References 28
Problems 29
CHAPTER 3 Measurement Systems with Electrical Signals 36
3.1 Electrical Signal Measurement Systems 36
3.2 Signal Conditioners 37
3.2.1 General Characteristics of Signal Amplification 38
3.2.2 Amplifiers Using Operational Amplifiers 44
3.2.3 Signal Attenuation 50
3.2.4 General Aspects of Signal Filtering 52
3.2.5 Butterworth Filters Using Operational Amplifiers 55
3.2.6 Circuits for Integration,Differentiation,and Comparison 59
3.3 Indicating and Recording Devices 60
3.3.1 Digital Voltmeters and Multimeters 60
3.3.2 Oscilloscopes 61
3.3.3 Strip-Chart Recorders 63
3.3.4 Data Acquisition Systems 64
3.4 Electrical Transmission of Signals Between Components 64
3.4.1 Low-Level Analog Voltage Signal Transmission 64
3.4.2 High-Level Analog Voltage Signal Transmission 67
3.4.3 Current-Loop Analog Signal Transmission 67
3.4.4 Digital Signal Transmission 68
References 68
Problems 68
iii
iv Contents
CHAPTER 4 Computerized Data-Acquisition Systems 71
4.1 Introduction 71
4.2 Computer Systems 72
4.2.1 Computer Systems for Data Acquisition 72
4.2.2 Components of Computer Systems 73
4.2.3 Representing Numbers in Computer Systems 75
4.3 Data-Acquisition Components 78
4.3.1 Multiplexers 78
4.3.2 Basics of Analog-to-Digital Converters 79
4.3.3 Practical Analog-to-Digital Converters 86
4.3.4 Digital-to-Analog Converters 90
4.3.5 Simultaneous Sample-and-Hold Subsystems 91
4.4 Configurations of Data-Acquisition Systems 92
4.4.1 Internal Single Board Plug-in Systems 92
4.4.2 External Systems 92
4.4.3 Digital Connectivity 93
4.4.4 Virtual Instruments 94
4.4.5 Digital Storage Oscilloscopes 95
4.4.6 Data Loggers 97
4.5 Software for Data-Acquisition Systems 97
4.5.1 Commercial Software Packages 98
References 98
Problems 99
CHAPTER 5 Discrete Sampling and Analysis of Time-Varying Signals 102
5.1 Sampling-Rate Theorem 102
5.2 Spectral Analysis of Time-Varying Signals 107
5.3 Spectral Analysis Using the Fourier Transform 112
5.4 Selecting the Sampling Rate and Filtering 119
5.4.1 Selecting the Sampling Rate 119
5.4.2 Use of Filtering to Limit Sampling Rate 121
References 124
Problems 125
CHAPTER 6 Statistical Analysis of Experimental Data 128
6.1 Introduction 128
6.2 General Concepts and Definitions 130
6.2.1 Definitions 130
6.2.2 Measures of Central Tendency 132
6.2.3 Measures of Dispersion 133
6.3 Probability 134
6.3.1 Probability Distribution Functions 135
6.3.2 Some Probability Distribution Functions with
Engineering Applications 139
6.4 Parameter Estimation 151
6.4.1 Interval Estimation of the Population Mean 152
6.4.2 Interval Estimation of the Population Variance 160
Contents v
6.5 Criterion for Rejecting Questionable Data Points 163
6.6 Correlation of Experimental Data 165
6.6.1 Correlation Coefficient 165
6.6.2 Least-Squares Linear Fit 169
6.6.3 Outliers in x–yData Sets 175
6.6.4 Linear Regression Using Data Transformation 178
6.6.5 Multiple and Polynomial Regression 180
6.7 Linear Functions of Random Variables 184
6.8 Applying Computer Software for Statistical Analysis
of Experimental Data 185
References 185
Problems 186
CHAPTER 7 Experimental Uncertainty Analysis 199
7.1 Introduction 199
7.2 Propagation of Uncertainties—General Considerations 199
7.3 Consideration of Systematic and Random Components
of Uncertainty 202
7.4 Sources of Elemental Error 209
7.5 Uncertainty of the Final Results for Multiple-Measurement
Experiments 214
7.6 Uncertainty of the Final Result for Single-Measurement
Experiments 218
7.7 Step-by-Step Procedure for Uncertainty Analysis 221
7.8 Interpreting Manufacturers’ Uncertainty Data 222
7.9 Applying Uncertainty Analysis in Digital
Data-Acquisition Systems 223
7.10 Additional Considerations for Single-Measurement
Experiments 227
7.11 Closure 230
References 230
Problems 230
CHAPTER 8 Measurement of Solid-Mechanical Quantities 244
8.1 Measuring Strain 244
8.1.1 Electrical Resistance Strain Gage 244
8.1.2 Strain Gage Signal Conditioning 249
8.2 Measuring Displacement 254
8.2.1 Potentiometer 254
8.2.2 Linear and Rotary Variable Differential Transformers 255
8.2.3 Capacitive Displacement Sensor 259
8.2.4 Digital Encoders 261
8.3 Measuring Linear Velocity 261
8.3.1 Linear Velocity Transducer 261
8.3.2 Doppler Radar Velocity Measurement 262
8.3.3 Velocity Determination Using Displacement
and Acceleration Sensors 263
vi Contents
8.4 Measuring Angular Velocity 264
8.4.1 Electric Generator Tachometers 264
8.4.2 Magnetic Pickup 265
8.4.3 Stroboscopic Tachometer 266
8.4.4 Photoelectric Tachometer 267
8.5 Measuring Acceleration and Vibration 267
8.5.1 Piezoelectric Accelerometers 267
8.5.2 Strain-Gage Accelerometers 270
8.5.3 Servo Accelerometer 271
8.5.4 Vibrometer 271
8.6 Measuring Force 272
8.6.1 Load Cells 272
8.6.2 Proving Rings 274
8.7 Measuring Rotating Shaft Torque 275
References 277
Problems 278
CHAPTER 9 Measuring Pressure,Temperature,and Humidity 284
9.1 Measuring Pressure 284
9.1.1 Traditional Pressure-Measuring Devices 284
9.1.2 Pressure Transducers 291
9.1.3 Measuring a Vacuum 293
9.2 Measuring Temperature 297
9.2.1 Thermocouples 297
9.2.2 Resistance-Temperature Detectors 304
9.2.3 Thermistor and Integrated-Circuit Temperature Sensors 308
9.2.4 Mechanical Temperature-Sensing Devices 310
9.2.5 Radiation Thermometers (Pyrometers) 312
9.2.6 Common Temperature-Measurement Errors 315
9.3 Measuring Humidity 321
9.3.1 Hygrometric Devices 321
9.3.2 Dew-Point Devices 322
9.3.3 Psychrometric Devices 322
9.4 Fiber-Optic Devices 324
9.4.1 Optical Fiber 324
9.4.2 General Characteristics of Fiber-Optic Sensors 326
9.4.3 Fiber-Optic Displacement Sensors 327
9.4.4 Fiber-Optic Temperature Sensors 328
9.4.5 Fiber Optic Pressure Sensors 330
9.4.6 Other Fiber-Optic Sensors 331
References 331
Problems 332
CHAPTER 10 Measuring Fluid Flow Rate,Fluid Velocity,Fluid Level,
and Combustion Pollutants 336
10.1 Systems for Measuring Fluid Flow Rate 336
10.1.1 Pressure Differential Devices 336
Contents vii
10.1.2 Variable-Area Flowmeters 352
10.1.3 Turbine Flowmeters 355
10.1.4 Mass Flowmeters 356
10.1.5 Positive-Displacement Flowmeters 359
10.1.6 Other Methods of Flow Measurement 359
10.1.7 Calibrating Flowmeters 363
10.2 Systems for Measuring Fluid Velocity 364
10.2.1 Pitot-Static Probe 364
10.2.2 Hot-Wire and Hot-Film Anemometers 366
10.2.3 Fluid Velocity Measurement Using the
Laser-Doppler Effect 368
10.3 Measuring Fluid Level 371
10.3.1 Buoyancy Devices 371
10.3.2 Differential-Pressure Devices 372
10.3.3 Capacitance Devices 373
10.3.4 Conductance Devices 374
10.3.5 Ultrasonic Devices 374
10.3.6 Weight Methods 375
10.4 Measuring Air Pollution Species 375
10.4.1 Nondispersive Infrared Detectors 376
10.4.2 Chemiluminescent Analyzers 378
10.4.3 Flame Ionization Detectors 379
10.4.4 Other Gas-Analysis Devices 380
10.4.5 General Considerations about Sampling
and Measuring Pollutant Gases 380
References 381
Problems 382
CHAPTER 11 Dynamic Behavior of Measurement Systems 387
11.1 Order of a Dynamic Measurement System 387
11.2 Zero-Order Measurement Systems 388
11.3 First-Order Measurement Systems 388
11.3.1 Basic Equations 389
11.3.2 Step Input 389
11.3.3 Ramp Input 390
11.3.4 Sinusoidal Input 392
11.3.5 Thermocouple as a First-Order System 392
11.4 Second-Order Measurement Systems 397
11.4.1 Basic Equations 397
11.4.2 Step Input 398
11.4.3 Sinusoidal Input 400
11.4.4 Force Transducer (Load Cell) as a Second-Order System 401
11.4.5 Pressure-Measurement Devices as Second-Order Systems 404
11.4.6 Second-Order Systems for Acceleration and Vibration 413
11.5 Closure 417
References 418
Problems 418
viii Contents
CHAPTER 12 Guidelines for Planning and Documenting Experiments 422
12.1 Overview of an Experimental Program 422
12.1.1 Problem Definition 422
12.1.2 Experiment Design 423
12.1.3 Experiment Construction and Development 423
12.1.4 Data Gathering 424
12.1.5 Data Analysis 424
12.1.6 Interpreting Data and Reporting 424
12.2 Common Activities in Experimental Projects 424
12.2.1 Dimensional Analysis and Determining the Test Rig Scale 424
12.2.2 Uncertainty Analysis 428
12.2.3 Shakedown Tests 428
12.2.4 Test Matrix and Test Sequence 429
12.2.5 Scheduling and Cost Estimation 433
12.2.6 Design Review 437
12.2.7 Documenting Experimental Activities 438
12.3 Closure 446
References 446
Answers to Selected Problems 447
APPENDIX A Computational Methods for Chapter 5 450
APPENDIX B Selected Properties of Substances 453
Glossary 458
Index 466
Preface
This book is an introduction to many of the topics that an engineer needs to master in
order to successfully design experiments and measurement systems.In addition to de-
scriptions of common measurement systems,the book describes computerized data ac-
quisition systems,common statistical techniques,experimental uncertainty analysis,and
guidelines for planning and documenting experiments.It should be noted that this book
is introductory in nature.Many of the subjects covered in a chapter or a few pages here
are the subjects of complete books or major technical papers.Only the most common
measurement systems are included—there exist many others that are used in practice.
More comprehensive studies of available literature and consultation with product ven-
dors are appropriate when engaging in a significant real-world experimental program.It
is to be expected that the skills of the experimenter will be enhanced by more advanced
courses in experimental and measurement systems design and practical experience.
The design of an experimental or measurement system is inherently an interdis-
ciplinary activity. For example, the instrumentation and control system of a process
plant might require the skills of chemical engineers, mechanical engineers, electrical
engineers,and computer engineers.Similarly,the specification of the instrumentation
used to measure the earthquake response of a large structure will involve the skills of
civil,electrical,and computer engineers.Based on these facts,the topics presented in
this book have been selected to prepare engineering students and practicing engineers
of different disciplines to design experimental projects and measurement systems.
This third edition of the book involves a general updating of the material and the
enhancement of the coverage in a number of areas.Specific enhancements include the
following:
● Addition of Windowing in the section on Fourier Transforms
● Addition of exponential and log-normal distributions
● Confidence interval estimation for linear regression
● Over 100 new homework problems
Two additional persons made contributions to the Third Edition.Brian S.Thurow,Auburn
University,contributed in the area of general instrumentation and V.V.Krishnan,San
Francisco State University,contributed material in statistics.
The book first introduces the essential general characteristics of instruments,
electrical measurement systems,and computerized data acquisition systems.This intro-
duction gives the students a foundation for the laboratory associated with the course.
The theory of discretely sampled systems is introduced next.The book then moves into
statistics and experimental uncertainty analysis,which are both considered central to a
modern course in experimental methods.It is not anticipated that the remaining chap-
ters will necessarily be covered either in their entirety or in the presented sequence in
lectures—the instructor will select appropriate subjects.Descriptions and theory are
provided for a wide variety of measurement systems.There is an extensive discussion
of dynamic measurement systems with applications.Finally,guidance for planning ex-
periments,including scheduling,cost estimation,and outlines for project proposals and
reports,are presented in the last chapter.
ix
