Instrumentation for Engineering Measurements-dally Jw, Rile Wf

INSTRUMENTATION FOR ENGINEERING MEASUREMENTS Second Edition

JAMES W. DALLY University of Maryland

WILLIAM F. RILEY KENNETH G. McCONNELL Iowa State University

JOHN WILEY & SONS, INC. New York • Chichester • Brisbane

• Toronto

•

Singapore

CONTENTS

LIST OF SYMBOLS CHAPTER 1 APPLICATIONS OF ELECTRONIC INSTRUMENT SYSTEMS 1.1 INTRODUCTION 1.2 THE ELECTRONIC INSTRUMENT SYSTEM 1.3 ENGINEERING ANALYSIS 1.4 PROCESS CONTROL 1.4.1 PROCESS CONTROL DEVICES 1.5 EXPERIMENTAL ERROR 1.5.1 ACCUMULATION OF ACCEPTED ERROR 1.5.2 IMPROPER FUNCTIONING OF INSTRUMENTS 1.5.3 EFFECT OF THE TRANSDUCER ON THE

1.6 1.7

R2 CHAPTER 2.1 2.2 2.3 2.4

2.5 2.6 2.7 2.8 2.9

xvii

01 01 02 03 04 06 12 13 14

PROCESS 1.5.4 DUAL SENSITIVITY ERRORS 1.5.5 OTHER SOURCES OF ERROR MINIMIZING EXPERIMENTAL ERROR SUMMARY REFERENCES EXERCISES

15 17 18 19 20 20 21

ANALYSIS OF CIRCUITS INTRODUCTION AND DEFINITIONS BASIC ELECTRICAL COMPONENTS KIRCHHOFF'S CIRCUIT LAWS DIODES, TRANSISTORS, AND GATES 2.4.1 DIODES 2.4.2 TRANSISTORS 2.4.3 GATES DC CIRCUITS PERIODIC FUNCTIONS AC CIRCUITS 2.7.1 IMPEDANCE FREQUENCY RESPONSE FUNCTION SUMMARY REFERENCES EXERCISES

24 24 26 28 29 29 29 31 33 34 38 40 42 44 45 45 vii

CONTENTS

CHAPTER 3 ANALOG RECORDING INSTRUMENTS 3.1 INTRODUCTION 3.2 GENERAL CHARACTERISTICS OF RECORDING INSTRUMENTS 3.3 VOLTMETERS FOR STEADY-STATE MEASUREMENTS 3.3.1 D'ARSONVAL GALVANOMETER 3.3.2 AMMETER 3.3.3 DC VOLTMETERS 3.3.4 VOLTMETER LOADING ERRORS 3.3.5 AMPLIFIED VOLTMETERS 3.3.6 POTENTIOMETRIC VOLTMETERS 3.4 VOLTMETERS FOR SLOWLY VARYING SIGNALS 3.4.1 STRIP-CHART RECORDERS 3.4.2 X-Y RECORDERS 3.5 VOLTMETERS FOR RAPIDLY VARYING SIGNALS 3.5.1 OSCILLOGRAPH RECORDERS 3.5.2 TRANSIENT RESPONSE OF GALVANOMETERS 3.5.3 PERIODIC SIGNAL RESPONSE OF GALVANOMETERS 3.5.4 OSCILLOSCOPES 3.5.5 MAGNETIC TAPE RECORDERS 3.6 SUMMARY REFERENCES EXERCISES CHAPTER 4 4.1 4.2 4.3 4.4 4.5

4.6 4.7 4.8 4.9 4.10 4.11 4.12

DIGITAL RECORDING SYSTEMS INTRODUCTION DIGITAL CODES CONVERSION PROCESSES DIGITAL-TO-ANALOG CONVERTERS ANALOG-TO-DIGITAL CONVERTERS 4.5.1 SUCCESSIVE-APPROXIMATION METHOD 4.5.2 INTERGRATION METHOD 4.5.3 PARALLEL OR FLASH METHOD DATA DISTRIBUTION 4.6.1 BUS STRUCTURES INTERFACES DIGITAL VOLTMETERS DATA-LOGGING SYSTEMS DATA-ACQUISITION SYSTEMS PC-BASED DATA-ACQUISITION SYSTEMS DIGITAL OSCILLOSCOPES

49 49 49 54 54 55 56 57 57 58 59 59 60 61 61 62 68 73 77 81 82 82 86 86 86 88 89 92 92 94 97 98 99 101 102 108 109 112 112

CONTENTS ix 4.13 4.14 4.15

CHAPTER 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

10 11 12 13 14

WAVEFORM RECORDERS ALIASING 4.14.1 ANTIALIASING FILTERS SUMMARY REFERENCES EXERCISES

116 117 119 119 120 120

SENSORS FOR TRANSDUCERS INTRODUCTION POTENTIOMETERS DIFFERENTIAL TRANSFORMERS RESISTANCE STRAIN GAGES CAPACITANCE SENSORS EDDY-CURRENT SENSORS PIEZOELECTRIC SENSORS PIEZORESISTIVE SENSORS PHOTOELECTRIC SENSORS 5.9.1 VACUUM-TUBE DETECTORS 5.9.2 PHOTOCONDUCTIVE CELLS 5.9.3 SEMICONDUCTOR PHOTODIODES RESISTANCE TEMPERATURE DETECTORS THERMISTORS THERMOCOUPLES CRYSTAL OSCILLATORS SUMMARY REFERENCES EXERCISES

124 124 124 126 129 135 137 139 142 144 146 149 149 151 152 153 155 157 157 158

CHAPTER 6 SIGNAL CONDITIONING CIRCUITS 6.1 INTRODUCTION 6.2 POWER SUPPLIES 6.2.1 BATTERY SUPPLIES 6.2.2 LINE VOLTAGE SUPPLIES 6.3 POTENTIOMETER CIRCUIT (CONSTANT VOLTAGE) 6.4 POTENTIOMETER CIRCUIT (CONSTANT CURRENT) 6.5 WHEATSTONE BRIDGE (CONSTANT VOLTAGE) 6.6 WHEATSTONE BRIDGE (CONSTANT CURRENT) 6.7 AMPLIFIERS 6.8 OPERATIONAL AMPLIFIERS 6.8.1 INVERTING AMPLIFIER 6.8.2 DIFFERENTIAL AMPLIFIER 6.8.3 VOLTAGE FOLLOWER 6.8.4 SUMMING AMPLIFIER

162 162 162 162 165 166 169 170 173 176 181 181 184 186 187

x

CONTENTS

6.9

6.10 6.11

6.12

CHAPTER 7 7.1 7.2 7.3 7.4 7.5

7.6 7.7

7.8 7.9 7.10 7.11

7.12

6.8.5 INTEGRATING AMPLIFIER 6.8.6 DIFFERENTIATING AMPLIFIER FILTERS 6.9.1 HIGH-PASS RC FILTER 6.9.2 LOW-PASS RC FILTER 6.9.3 ACTIVE FILTER AMPLITUDE MODULATION AND DEMODULATION TIME-MEASURING CIRCUITS 6.11.1 BINARY COUNTING UNIT 6.11.2 GATES IN COUNTER APPLICATIONS 6.11.3 TRIGGERS 6.11.4 COUNTING INSTRUMENTS SUMMARY REFERENCES EXERCISES RESISTANCE-TYPE STRAIN GAGES INTRODUCTION ETCHED-FOIL STRAIN GAGES STRAIN-GAGE INSTALLATION WHEATSTONE BRIDGE SIGNAL CONDITIONING RECORDING INSTRUMENTS FOR STRAIN GAGES 7.5.1 DIRECT-READING STRAIN INDICATOR 7.5.2 NULL-BALANCE BRIDGES 7.5.3 STRAIN-GAGE SIGNAL CONDITIONERS 7.5.4 WHEATSTONE BRIDGE AND OSCILLOSCOPE 7.5.5 WHEATSTONE BRIDGE AND OSCILLOGRAPH CALIBRATION METHODS EFFECTS OF LEAD WIRES, SWITCHES, AND SLIP RINGS 7.7.1 LEAD WIRES 7.7.2 SWITCHES 7.7.3 SLIP RINGS ELECTRICAL NOISE TEMPERATURE-COMPENSATED GAGES ALLOY SENSITIVITY, GAGE FACTOR, AND CROSS-SENSITIVITY FACTORS DATA-REDUCTION METHODS 7.11.1 THE UNIAXIAL STATE OF STRESS 7.11.2 THE BIAXIAL STATE OF STRESS 7.11.3 THE GENERAL STATE OF STRESS HIGH-TEMPERATURE STRAIN MEASUREMENTS

188 189 189 190 191 193 194 197 197 198 198 199 202 205 206 211 211 212 212 214 219 220 220 222 222 224 227 229 229 232 234 234 236 238 241 241 242 242 244

CONTENTS xi 7.13

CHAPTER 8 8.1 8.2

8.3

8.4

8.5

SUMMARY REFERENCES EXERCISES FORCE, TORQUE, AND PRESSURE MEASUREMENTS INTRODUCTION FORCE MEASUREMENTS (LOAD CELLS) 8.2.1 LINK-TYPE LOAD CELL 8.2.2 BEAM-TYPE LOAD CELL 8.2.3 RING-TYPE LOAD CELL 8.2.4 SHEAR-WEB-TYPE LOAD CELL TORQUE MEASUREMENT (TORQUE CELLS) 8.3.1 TORQUE CELLS - DESIGN CONCEPTS 8.3.2 TORQUE CELLS-DATA TRANSMISSION COMBINED MEASUREMENTS OF FORCE AND MOMENTS OR TORQUES 8.4.1 FORCE-MOMENT MEASUREMENTS 8.4.2 FORCE-TORQUE MEASUREMENTS PRESSURE MEASUREMENTS (PRESSURE TRANSDUCERS) 8.5.1 DISPLACEMENT-TYPE PRESSURE

TRANSDUCER 8.5.2

245 248 249

253 253 253 254 256 258 260 262 262 264 268 268 271 271 272

DIAPHRAGM-TYPE PRESSURE

TRANSDUCER

272

8.5.3

8.6

8.7

8.9

CHAPTER 9 9.1 9.2

PIEZOELECTRIC-TYPE PRESSURE TRANSDUCER MINIMIZING ERRORS IN TRANSDUCERS 8.6.1 DUAL SENSITIVITY 8.6.2 ZERO SHIFT WITH TEMPERATURE CHANGE 8.6.3 BRIDGE BALANCE 8.6.4 SPAN ADJUST 8.6.5 SPAN CHANGE WITH TEMPERATURE FREQUENCY RESPONSE OF TRANSDUCERS 8.7.1 RESPONSE OF A FORCE TRANSDUCER TO A TERMINATED RAMP FUNCTION 8.7.2 RESPONSE OF A FORCE TRANSDUCER TO A SINUSOIDAL FORCING FUNCTION CALIBRATION OF TRANSDUCERS SUMMARY REFERENCES EXERCISES

285 286 288 289 290

DISPLACEMENT, VELOCITY, AND ACCELERATION MEASUREMENTS INTRODUCTION THE SEISMIC TRANSDUCER MODEL

293 293 294

275 276 277 279 280 280 280 280 282

xii

CONTENTS

9.3

9.4

9.5 9.6

9.7 9.8 9.9

9.10 9.11 9.12

9.13

9.14

9.15

DYNAMIC RESPONSE OF THE SEISMIC MODEL 9.3.1 SINUSOIDAL EXCITATION 9.3.2 TRANSIENT EXCITATIONS SEISMIC MOTION TRANSDUCERS 9.4.1 SEISMIC DISPLACEMENT TRANSDUCERS 9.4.2 SEISMIC VELOCITY TRANSDUCERS 9.4.3 SEISMIC ACCELERATION TRANSDUCERS PIEZOELECTRIC FORCE TRANSDUCERS PIEZOELECTRIC SENSOR CIRCUITS 9.6.1 CHARGE SENSITIVITY MODEL 9.6.2 VOLTAGE-FOLLOWER CIRCUIT 9.6.3 CHARGE-AMPLIFIER CIRCUIT 9.6.4 BUILT-IN VOLTAGE FOLLOWERS RESPONSE OF PIEZOELECTRIC CIRCUITS TO TRANSIENT SIGNALS ACCELEROMETER CALIBRATION DYNAMIC CALIBRATION OF FORCE TRANSDUCERS 9.9.1 FORCE TRANSDUCER CALIBRATION BY IMPACT OVERALL SYSTEM CALIBRATION SOURCES OF ERROR WITH PIEZOELECTRIC TRANSDUCERS DISPLACEMENT MEASUREMENTS IN A FIXED REFERENCE FRAME 9.12.1 DISPLACEMENT MEASUREMENTS WITH RESISTANCE POTENTIOMETERS 9.12.2 DISPLACEMENT MEASUREMENTS WITH MULTIPLE-RESISTOR DEVICES 9.12.3 PHOTOELECTRIC DISPLACEMENT TRANSDUCERS OPTICAL DISPLACEMENT MEASUREMENTS 9.13.1 OPTICAL TRACKER SYSTEM 9.13.2 VIDEO CAMERA MOTION ANALYSIS VELOCITY MEASUREMENTS 9.14.1 LINEAR-VELOCITY MEASUREMENTS 9.14.2 ANGULAR-VELOCITY MEASUREMENTS 9.14.3 LASER-DOPPLER SYSTEM SUMMARY REFERENCES EXERCISES

295 295 298 299 300 301 301 305 306 306 308 311 313 317 320 323 325 327 328 331 331 335 336 337 337 338 339 340 342 343 344 345 347

CONTENTS

xiii

CHAPTER 10 ANALYSIS OF VIBRATING SYSTEMS 356 10.1 INTRODUCTION 356 10.1.1 TEMPORAL MEAN 358 10.1.2 TEMPORAL MEAN SQUARE AND ROOT MEAN SQUARE 358 10.2 SINUSOIDAL SIGNAL ANALYSIS 358 10.3 CHARACTERISTICS OF SIGNALS 3 61 10.3.1 PERIODIC SIGNALS 362 10.3.2 TRANSIENT SIGNALS 363 10.3.3 RANDOM SIGNALS 366 10.4 LUMPED MASS-SPRING VIBRATION MODELS 368 10.4.1 UNDAMPED NATURAL FREQUENCY AND MODE SHAPE 369 10.4.2 FORCED VIBRATION RESPONSE (DIRECT SOLUTION) 370 10.4.3 FORCED VIBRATION RESPONSE (MODAL SOLUTION) 370 10.5 CONTINUOUS VIBRATION MODELS 373 10.5.1 FUNDAMENTAL EQUATION OF MOTION 373 10.5.2 STEADY-STATE MODAL SOLUTION 374 10.6 THE LINEAR INPUT-OUTPUT MODEL 376 10.6.1 IMPULSE RESPONSE 377 10.6.2 RANDOM INPUT-OUTPUT RELATIONSHIPS 379 10.7 BASICS OF A DIGITAL FREQUENCY ANALYZER 380 10.7.1 TIME SAMPLING PROCESS 380 10.7.2 CONVOLUTION 381 10.7.3 FILTER LEAKAGE 385 10.7.4 BLOCK DIAGRAM 387 10.8 USING A DIGITAL FREQUENCY ANALYZER 387 10.8.1 RELATIONSHIPS FOR FREQUENCY ANALYZERS 388 10.8.2 FILTER CHARACTERISTICS 390 10.8.3 FOUR COMMON WINDOW FUNCTIONS 392 10.8.4 UNCERTAINTY IN THE MAGNITUDE OF SPECTRAL LINES 394 10.8.5 SUMMARY OF WINDOW USE 395 10.9 ACCELEROMETER CROSS-AXIS SENSITIVITY 396 10.9.1 SINGLE ACCELEROMETER CROSS-AXIS COUPLING MODEL 396 10.9.2 TRIAXIAL ACCELEROMETER MODEL 397 10.9.3 CORRECTING ACCELERATION VOLTAGE READINGS 397

xiv

CONTENTS

10.9.4

10.10

10.11

APPLICATION TO MODAL ANALYSIS SIGNALS 10.9.5 CROSS-AXIS RESONANCE FORCE TRANSDUCER-STRUCTURE INTERACTION 10.10.1 GENERAL TWO-DEGREE-OF-FREEDOM FORCE TRANSDUCER MODEL SUMMARY REFERENCES EXERCISES

399 399 400 401 406 408 409

CHAPTER 11 TEMPERATURE MEASUREMENTS 412 11.1 INTRODUCTION 412 11.2 EXPANSION METHODS FOR MEASURING TEMPERATURE 415 11.3 RESISTANCE THERMOMETERS 416 11.3.1 RESISTANCE TEMPERATURE DETECTORS (RTDS) 417 11.3.2 RTDS AND THE WHEATSTONE BRIDGE 420 11.3.3 THERMISTORS 424 11.4 THERMOCOUPLES 428 11.4.1 PRINCIPLES OF THERMOCOUPLE BEHAVIOR 430 11.4.2 THERMOELECTRIC MATERIALS 434 11.4.3 REFERENCE IUNCTION TEMPERATURE 437 11.4.4 FABRICATION AND INSTALLATION PROCEDURES 439 11.4.5 RECORDING INSTRUMENTS FOR THERMOCOUPLES 442 11.4.6 NOISE SUPPRESSION IN THERMOCOUPLE CIRCUITS 444 11.5 INTEGRATED-CIRCUIT TEMPERATURE SENSORS 444 11.6 DYNAMIC RESPONSE OF TEMPERATURE SENSORS 446 11.7 SOURCES OF ERROR IN TEMPERATURE MEASUREMENTS 449 11.8 CALIBRATION METHODS 453 11.9 RADIATION METHODS (PYROMETRY) 454 11.9.1 PRINCIPLES OF RADIATION 454 11.9.2 THE OPTICAL PYROMETER 456 11.9.3 INFRARED PYROMETERS 458 11.9.4 PHOTON DETECTOR TEMPERATURE INSTRUMENTS 460 11.10 SUMMARY 463 REFERENCES 465 EXERCISES 466

CONTENTS

CHAPTER 12 12.1 12.2

12.3

12.4 12.5

12.6 12.7

12.8

FLUID FLOW MEASUREMENTS INTRODUCTION FLOW VELOCITY (INSERTION-TYPE TRANSDUCERS) 12.2.1 PITOT TUBE (INCOMPRESSIBLE FLOW) 12.2.2 PITOT TUBE (COMPRESSIBLE FLOW) 12.2.3 HOT-WIRE AND HOT-FILM ANEMOMETERS 12.2.4 DRAG-FORCE VELOCITY TRANSDUCERS 12.2.5 CURRENT METERS 12.2.6 TURBINE FLOW METERS 12.2.7 VORTEX-SHEDDING TRANSDUCERS FLOW RATES IN CLOSED SYSTEMS BY PRESSURE-VARIATION MEASUREMENTS 12.3.1 VENTURI METER 12.3.2 FLOW NOZZLE 12.3.3 ORIFICE METER 12.3.4 ELBOW METER FLOW RATES IN PARTIALLY CLOSED SYSTEMS FLOW RATES IN OPEN CHANNELS FROM PRESSURE MEASUREMENTS 12.5.1 SLUICEGATE 12.5.2 WEIRS COMPRESSIBLE FLOW EFFECTS IN CLOSED SYSTEMS OTHER FLOW-MEASUREMENT METHODS FOR CLOSED SYSTEMS 12.7.1 CAPILLARY FLOW METER 12.7.2 POSITIVE-DISPLACEMENT FLOW METERS 12.7.3 HOT-FILM MASS FLOW TRANSDUCERS 12.7.4 LASER VELOCIMETRY SYSTEMS SUMMARY REFERENCES EXERCISES

CHAPTER 13 STATISTICAL METHODS 13.1 INTRODUCTION 13.2 CHARACTERIZING STATISTICAL DISTRIBUTIONS 13.2.1 GRAPHIC REPRESENTATIONS OF THE DISTRIBUTION 13.2.2 MEASURES OF CENTRAL TENDENCY 13.2.3 MEASURES OF DISPERSION 13.3 STATISTICAL DISTRIBUTION FUNCTIONS 13.3.1 GAUSSIAN DISTRIBUTION 13.3.2 WEIBULL DISTRIBUTION

xv

473 473 476 476 479 481 486 489 491 492 493 494 495 496 498 499 500 500 501 503 504 504 505 506 507 512 512 514 521 521 522 522 524 524 526 526 529

CONTENTS

13.4 CONFIDENCE INTERVALS FOR PREDICTIONS 13.5 COMPARISION OF MEANS 13.6 STATISTICAL CONDITIONING OF DATA 13.7 REGRESSION ANALYSIS 13.7.1 LINEAR REGRESSION ANALYSIS 13.7.2 MULTIVARIATE REGRESSION 13.8 CHI-SQUARE TESTING 13.9 ERROR ACCUMULATION AND PROPAGATION 13.10 SUMMARY REFERENCES EXERCISES

532 537 537 538 539 541 544 545 548 549 550

APPENDIX A

558

APPENDIX В

572

AUTHOR INDEX

577

SUBJECT INDEX

579