(3rd Edition) Anthony J. Wheeler, Ahmad R. Ganji Introduction to Engineering Experimentation Prentice Hall (2009) PDF

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I

UNIVERSAL CONSTANTS Standard Gravitational Acceleration

g

Speed of Light

c

Stefan-Boltzmann Constant

= =

u =

R

Universal Gas constant

= = = =

9.80665 m/s2 = 32.1 742 ft/s2 2.998 X 1 08 mls 5.670 X 10-8 W/m2.K4 0.1712 X 10-8 Btu/h.ft2.R4 8314.4 J/kg mole.K 1 .9859 BtullbmoIe.R 1 545.35 ft.lbfllbmole.R

CONVERSION FACTORS To convert from Energy

Btu

J

cal

J

ft.lbf

Btu

hp.h

Btu

dyn

N N

kWh

Force

kJ

Ibf Thermal conductivity

Btulh.fLF

Heat transfer coefficient

Btulh.fe.F

Length

[t

m cm

m

Power

cm

m

mile

km

Ibm

kg

slug

Ibm

ton (metric)

kg

ton (metric)

Ibm

ton (short)

Ibm

Btulh

W

Btuls

W

hp Pressure

W

hp

ft.lbf/s

atm

kPa

bar

kPa

Ibflin2 (psi)

kPa

atm

psi

atm

cm Hg atOC

atm Temperature

Deg.K

Volume

cm3

1

Deg. R ft3

gallon (US) liter

C to Oeg. K F to Ocg. C Oeg. F to Oeg. R Oeg.

Oeg.

Oeg.

Oeg. Ocg.

K C R

be used

C

F - 32) 459.67

=

Oeg.

(5/9)(Oeg.

=

Oeg.

F

+ 273.15

+

1 055.0 4.186 3600 0.00128507 2545 10-5 4.4482 1 .7307 5.6782 0.3048 2.540 100 10-6 1 .60934 0.4536 32.174 1000 2204.6 2000 0.293 1055.04 745.7 550 101 .325 1 00 6.895

ft3 m3

1 0-3

em H 0 at4 C 2 R

K

m3 m3

for temperature conversion:

=

Multiply by

14.696 76.0 1 033.2 9/5 5/9 10-6 0.02832 0.0037854 0.13368

m3

gallon (US)

Ilbe following relations should

W/m.C

W/m2.C

in J-Lm Mass

To

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Library of Congress Cataloging-in-Publication Data

Wheeler, Anthony 1. I� troducti? n t? engineering experimentation / Anthony 1. Wheeler, Ahmad R. Ganji; wIth contnbutIOns by V. V. Krishnan, Brian S. Thurow. -3rd ed. p.cm. Includes bibliographical references and index. ISBN 978-0-13-174276-5 (alk. paper) l. Engineering-Experiments. 2. Experimental design. I . GanJ'i , A .. R (Ahmad R eza) II Title "

TA153.W472004

2009045089

620.0078-dc22

Prentice Hall is an imprint of

PEARSON

WWW.pearsonhighere

d.com

ISBN-13:

ISBN-l0:

1 0 9 8 7 (1 I I

978-0-13-1711

0-13-17427bl

I

I I I I I I I I I I I I

l

i

i

I

Contents ix

Preface CHAPTER 1

Introduction

1.1

Applications of Engineering Experimentation and Measurement 1.1.1 Measurement in Engineering Experimentation 1.1.2 Measurement in Operational Systems 1.2 Objective and Overview Dimensions and Units 1.3 Closure . 1.4 Problems CHAPTER 2

General Characteristics of Measurement Systems

2.1 2.2

Generalized Measurement System Validity of Measurement 2.2.1 Measurement Error and Related Definitions 2.2.2 Calibration of Measurement Systems Dynamic Measurements 2.3 2.4 Closure References Problems

CHAPTER

3

Measurement Systems with Electrical Signals

3.1 3.2

Electrical Signal Measurement Systems Signal Conditioners 3.2.1 General Characteristics of Signal Amplification 3.2.2 Amplifiers Using Operational Amplifiers 3.2.3 Signal Attenuation 3.2.4 General Aspects of Signal Filtering 3.2.5 Butterworth Filters Using Operational Amplifiers 3.2.6 Circuits for Integration, Differentiation, and Comparison Indicating and Recording Devices 3.3 3.3.1 Digital Voltmeters and Multimeters 3.3.2 Oscilloscopes 3.3.3 Strip-Chart Recorders 3.3.4 Data Acquisition Systems 3.4 Electrical Transmission of Signals Between Components 3.4.1 Low-Level Analog Voltage Signal Transmission 3.4.2 High-Level Analog Voltage Signal Transmission 3.4.3 Current-Loop Analog Signal Transmission 3.4.4 Digital Signal Transmission References Problems

1

1 1 3 3 4 5 5 7

7

8 9 16 24 28 28 29 36

36 37 38 44 50 52 55 59 60 60 61 63 64 64 64 67 67 68 68 68 iii

iv

Contents

CHAPTER

4

Computerized Data-Acquisition Systems

4.1 4.2

Introduction Computer Systems 4.2.1 Computer Systems for Data Acquisition 4.2.2 Components of Computer Systems 4.2.3 Representing Numbers in Computer Systems 4.3 Data-Acquisition Components 4.3.1 Multiplexers 4.3.2 Basics of Analog-to-Digital Converters 4.3.3 Practical Analog-to-Digital Converters 4.3.4 Digital-to-Analog Converters 4.3.5 Simultaneous Sample-and-Hold Subsystems 4.4 Configurations of Data-Acquisition Systems 4.4.1 Internal Single Board Plug-in Systems 4.4.2 External Systems 4.4.3 Digital Connectivity 4.4.4 Virtual Instruments 4.4.5 Digital Storage Oscilloscopes 4.4.6 Data Loggers 4.5 Software for Data-Acquisition Systems 4.5.1 Commercial Software Packages References Problems CHAPTER

5

Discrete Sampling and Analysis of TIme-Varying Signals

5.1 5.2 5.3 5.4

Sampling-Rate Theorem Spectral Analysis of Time-Varying Signals Spectral Analysis Using the Fourier Transform Selecting the Sampling Rate and Filtering 5.4.1 Selecting the Sampling Rate 5.4.2 Use of Filtering to Limit Sampling Rate References Problems

CHAPTER 6

Statistical Analysis of Experimental Data

6.1 6.2

6.3

6.4

Introduction General Concepts and Definitions 6.2.1 Definitions 6.2.2 Measures of Central Tendency 6.2.3 Measures of Dispersion Probability 6.3.1 Probability Distribution Functions 6.3.2 Some Probability Distribution Functions with Engineering Applications Parameter Estimation 6.4. 1 Interval Estimation of the Population Mean 6.4.2 Interval Estimation of the Population Variance

71

71 72 72 73 75 78 78 79 86 90 91 92 92 92 93 94 95 97 97 98 98 99 102

102 107 112 119 119 121 124 125 128

128 130 130 132 133 134 135 139 151 152 160

Contents

6.5 6.6

Criterion for Rejecting Questionable Data Points Correlation of Experimental Data 6.6.1 Correlation Coefficient 6.6.2 Least-Squares Linear Fit 6.6.3 Outliers in x-y Data Sets 6.6.4 Linear Regression Using Data Transformation 6.6.5 Multiple and Polynomial Regression 6.7 Linear Functions of Random Variables 6.8 Applying Computer Software for Statistical Analysis of Experimental Data References Problems

CHAPTER 7

Experimental Uncertainty Analysis

7.1 7.2 7.3

Introduction Propagation of Uncertainties - General Considerations Consideration of Systematic and Random Components of Uncertainty 7.4 Sources of Elemental Error 7.5 Uncertainty of the Final Results for Multiple-Measurement Experiments 7.6 Uncertainty of the Final Result for Single-Measurement Experiments 7.7 Step-by-Step Procedure for Uncertainty Analysis 7.8 Interpreting Manufacturers' Uncertainty Data Applying Uncertainty Analysis in Digital 7.9 Data-Acquisition Systems 7.10 Additional Considerations for Single-Measurement Experiments 7.11 Closure References Problems CHAPTER

8

Measurement of Solid-Mechanical Quantities

8.1

8.2

8.3

Measuring Strain 8.1.1 Electrical Resistance Strain Gage 8.1.2 Strain Gage Signal Conditioning Measuring Displacement 8.2.1 Potentiometer 8.2.2 Linear and Rotary Variable Differential Transformers 8.2.3 Capacitive Displacement Sensor 8.2.4 Digital Encoders Measuring Linear Velocity 8.3.1 Linear Velocity Transducer 8.3.2 Doppler Radar Velocity Measurement 8.3.3 Velocity Determination Using Displacement and Acceleration Sensors

v

163 165 165 169 175 178 180 184 185 185 186 199

199 199 202 209 214 218 221 222 223 227 230 230 230 244

244 244 249 254 254 255 259 261 261 261 262 263

vi

Contents

8.4

Measuring Angular Velocity 8.4. 1 Electric Generator Tachometers 8.4.2 Magnetic Pickup 8.4.3 Stroboscopic Tachometer 8.4.4 Photoelectric Tachometer 8.5 Measuring Acceleration and Vibration 8.5.1 Piezoelectric Accelerometers 8.5.2 Strain-Gage Accelerometers 8.5.3 Servo Accelerometer 8.5.4 Vibrometer 8.6 Measuring Force 8.6.1 Load Cells 8.6.2 Proving Rings 8.7 Measuring Rotating Shaft Torque References Problems CHAPTER

9

Measuring Pressure, Temperature, and Humidity

9.1

Measuring Pressure 9.1.1 Traditional Pressure-Measuring Devices 9.1.2 Pressure Transducers 9. 1 .3 Measuring a Vacuum 9.2 Measuring Temperature 9.2.1 Thermocouples 9.2.2 Resistance-Temperature Detectors 9.2.3 Thermistor and Integrated-Circuit Temperature Sensors 9.2.4 Mechanical Temperature-Sensing Devices 9.2.5 Radiation Thermometers (Pyrometers ) 9.2.6 Common Temperature-Measurement Errors 9.3 Measuring Humidity 9.3.1 Hygrometric Devices 9.3.2 Dew-Point Devices 9.3.3 Psychrometric Devices 9.4 Fiber-Optic Devices 9.4.1 Optical Fiber 9.4.2 General Characteristics of Fiber-Optic Sensors 9.4.3 Fiber-Optic Displacement Sensors 9.4.4 Fiber-Optic Temperature Sensors 9.4.5 Fiber Optic Pressure Sensors 9.4.6 Other Fiber-Optic Sensors References Problems

CHAPTER 1 0

Measuring Fluid Flow Rate, Fluid Velocity, Fluid Level, and Combustion Pollutants

10.1

Systems for Measuring Fluid Flow Rate 10.1.1 Pressure Differential Devices

264 264 265 266 267 267 267 270 271 271 272 272 274 275 277 278 284

284 284 291 293 297 297 304 308 310 312 315 321 321 322 322 324 324 326 327 328 330 331 331 332

336

336 336

Contents

10.1.2 Variable-Area Flowmeters 10.1.3 Thrbine Flowmeters 10.1.4 Mass Flowmeters 10.1.5 Positive-Displacement Flowmeters 10.1.6 Other Methods of Flow Measurement 10.1.7 Calibrating Flowmeters 10.2 Systems for Measuring Fluid Velocity 10.2.1 Pitot-Static Probe 10.2.2 Hot-Wire and Hot-Film Anemometers 10.2.3 Fluid Velocity Measurement Using the Laser-Doppler Effect 10.3 Measuring Fluid Level 10.3.1 Buoyancy Devices 10.3.2 Differential-Pressure Devices 10.3.3 Capacitance Devices 10.3.4 Conductance Devices 10.3.5 Ultrasonic Devices 10.3.6 Weight Methods 10.4 Measuring Air Pollution Species 10.4.1 Nondispersive Infrared Detectors 10.4.2 Chemiluminescent Analyzers 10.4.3 Flame Ionization Detectors 10.4.4 Other Gas-Analysis Devices 10.4.5 General Considerations about Sampling and Measuring Pollutant Gases References Problems

CHAPTER 1 1

Dynamic Behavior of Measurement Systems

11.1 11.2 11.3

Order of a Dynamic Measurement System Zero-Order Measurement Systems First-Order Measurement Systems 11.3.1 Basic Equations 11.3.2 Step Input 11 .3.3 Ramp Input 11.3.4 Sinusoidal Input 11.3.5 Thermocouple as a First-Order System 11.4 Second-Order Measurement Systems 11.4.1 Basic Equations 11.4.2 Step Input 11.4.3 Sinusoidal Input 1 1 .4.4 Force Transducer (Load Cell) as a Second-Order System 11 .4.5 Pressure-Measurement Devices as Second-Order Systems 11.4.6 Second-Order Systems for Acceleration and Vibration 11.5 Closure References Problems

vii

352 355 356 359 359 363 364 364 366 368 371 371 372 373 374 374 375 375 376 378 379 380 380 381 382

387

387 388 388 389 389 390 392 392 397 397 398 400 401 404 413 417 418 418

viii

Contents

CHAPTER 12

Guidelines for Planning and Documenting Experiments

12.1

Overview of an Experimental Program 12.1.1 Problem Definition 12.1.2 Experiment Design 12.1.3 Experiment Construction and Development 12.1.4 Data Gathering 12.1.5 Data Analysis 12.1.6 Interpreting Data and Reporting 12.2 Common Activities in Experimental Projects 12.2.1 Dimensional Analysis and Determining the Test Rig Scale 12.2.2 Uncertainty Analysis 12.2.3 Shakedown Tests 12.2.4 Test Matrix and Test Sequence 12.2.5 Scheduling and Cost Estimation 12.2.6 Design Review 12.2.7 Documenting Experimental Activities 12.3 Closure References Answers to Selected Problems

422

422 422 423 423 424 424 424 424 424 428 428 429 433 437 438 446 446 447

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

1\vo 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 modem 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

x

Preface

There are some subjects included in the introductory chapters that are frequent­ ly of interest, but are often not considered vital for an introductory experimental meth­ ods course. These subjects include the material on circuits using operational amplifiers (Sections 3.2.2, 3.2.5 and 3.2.6), details on various types of analog-to-digital converters (Section 4.3.3), and the material on Fourier transforms (Section 5.3). Any or all of these sections can be omitted without significant impact on the remainder of the text. The book has been designed for a semester course of up to three lectures with one laboratory per week. Depending on the time available, it is expected that only selected topics will be covered. The material covered depends on the number of lectures per week, the prior preparation of students in the area of statistics, and the scope of included design project(s). The book can serve as a reference for subsequent laboratory courses. Our introductory course in engineering experimentation is presented to all under­ graduate engineers in civil, electrical, and mechanical engineering. The one-semester format includes two lectures per week and one three-hour laboratory. In our two­ lecture-per-week format, the course content is broken dow...