Preface... (vii) Acknowledgement... (ix)

Preface... (vii) Acknowledgement... (ix) Chapter 1 Measurement Systems An Overview and Basic Concepts 1 1.1 Introduction 4 1.2 The Process of Measurement 4 1.3 Scope of Instrumentation 7 1.4 Jargon of Instrumentation 9 1.5 Basic Principles of Measurement 9 1.5.1 Direct Comparison 9 1.5.2 Indirect Comparison 10 1.6 Complexity of Measurement Methods 10 1.6.1 Primary Measurement 10 1.6.2 Secondary Measurement 11 1.6.3 Tertiary Measurement 11 1.7 Applications of Measuring Instruments 12 1.7.1 Instruments for Monitoring 12 1.7.2 Instruments for Controlling 12 1.7.3 Instruments for Experiments and Analysis 12 1.8 Generalized Input-Output Model of Measurement System 13 1.8.1 Stages of the Measuring System 16 1.9 Types of Inputs 20 1.9.1 Desired Inputs 20 1.9.2 Interfering Inputs 20 1.9.3 Modifying Inputs 20 1.10 Classification of Instruments 21 1.10.1 Manual and Automatic Instruments 21 1.10.2 Active (Self-operated) and Passive (Power-operated) Instruments 21 1.10.3 Self-contained and Remote Indicating Instruments 22 1. The extent or degree of 1.10.4 illumination Deflection (luminous and Null intensity) Output is Instruments measured in 22the units Candela. 1.10.5 Analog and Digital Instruments 23 1.10.6 Detecting, Recording, Monitoring and Controlling Instruments 23 1.10.7 Mechanical, Electrical and Electronic Instruments 24

(xii) Contents 1.11 Objectives of Instrumentation 25 Summary 26 Key Concepts 27 Review Questions 29 Multiple Choice Questions 31 Answers 33 Chapter 2 Characteristics of Instruments 35 2.1 Introduction 38 2.2 Static and Dynamic Quantities 38 2.3 Static Characteristics 39 2.3.1 Range 40 2.3.2 Span 40 2.3.3 Accuracy 40 2.3.4 Precision 40 2.3.5 Calibration 41 2.3.6 Drift 42 2.3.7 Sensitivity 42 2.3.8 Threshold 44 2.3.9 Resolution 44 2.3.10 Tolerance 44 2.3.11 Readability and Least Count 44 2.3.12 Backlash 44 2.3.13 Zero Stability 44 2.3.14 Stiction (Static Friction) 44 2.4 Dynamic Characteristics 45 2.4.1 Speed of Response and Measuring Lag 45 2.4.2 Fidelity and Dynamic Error 46 2.4.3 Overshoot 46 2.4.4 Dead Time and Dead Zone 46 2.4.5 Frequency of Response 46 2.5 Modeling for Dynamic Performance 46 2.6 Systems of Various Orders 49 2.6.1 Zero Order System 49 2.6.2 First Order System 50 2.6.3 Second Order System 50 2.7 Standard Test Signals 52 2.7.1 Step Signal 52 2.7.2 Ramp Signal 52 2.7.3 Parabolic Signal 52 2.7.4 Simple Harmonic Input (Sinusoidal) 53 2.7.5 Impulse Signal 53 2.8 Dynamic Response of First Order System 54 2.8.1 Unit Step Response of First Order System (Step Input) 54 2.8.2 Unit Ramp Response of First Order System (Ramp Input) 60 2.8.3 Harmonic Sinusoidal Response of First Order System 61

(xiii) 2.9 Dynamic Response of Second Order System 62 2.9.1 Step Response of Second Order System 63 2.9.2 Harmonic/Sinusoidal Response of Second Order System 64 Summary 67 Key Concepts 67 Review Questions 69 Multiple Choice Questions 71 Answers 73 Chapter 3 Inaccuracies in Instruments 75 3.1 Introduction 78 3.2 Terminology 78 3.2.1 Terms used to Describe Inaccuracy in the Instrument 78 3.3 Error of Measurement and Measurement of Error 79 3.3.1 Error of Measurement 79 3.3.2 Measurement of Errors 81 3.4 Error 82 3.5 Sources/Causes of Error 82 3.6 Classification of Errors 83 3.7 Random Errors (or Precision or Accidental Error) 85 3.7.1 Disturbance in the Equipment 86 3.7.2 Fluctuating Experimental or Environmental Conditions 86 3.8 Systematic Error (or Bias Error) 87 3.8.1 Calibration Error 87 3.8.2 Gross Errors or Human Errors 88 3.8.3 Operational Errors 89 3.8.4 Observation Errors 90 3.8.5 Equipment Defects and Instrumental Errors 90 3.8.6 Inherent Defects 91 3.8.7 Misusing or Mishandling Errors 92 3.8.8 Loading Errors 92 3.9 Illegitimate Errors 93 3.9.1 Blunders and Chaotic Errors 93 3.10 Other Errors 93 3.10.1 Backlash 94 3.10.2 Mechanical Friction 94 3.10.3 Hysteresis 94 3.10.4 Drift 94 3.10.5 Reading Error 95 Summary 95 Key Concepts 96 Review Questions 98 Multiple Choice Questions 98 Answers 100

(xiv) Contents Chapter 4 Transducers and Measurement of Displacement 101 4.1 Introduction 104 4.2 Classification of Transucers 104 4.3 Mechanical Transducers 108 4.4 Electromechanical Transducers 111 4.4.1 Merits 111 4.4.2 Classification of Electromechanical Transducers 112 4.5 Resistive Type Transducers 112 4.5.1 Variable Resistance Transducers 113 4.5.2 Sliding Contact Devices The Pots 114 4.5.3 The Resistance Strain Gauges 116 4.5.4 Thermistors 116 4.6 Inductive Type Transducers 117 4.6.1 Non-Self-Generating Variable Self Inductance-Single Coil Type Transducer 118 4.6.2 Non-Self-Generating Variable Self Inductance Two Coil (or Single Coil with Center Tap) Type Transducer 118 4.6.3 Non-Self-Generating Variable Mutual Inductance Two Coil Transducer 119 4.6.4 Non-Self-Generating Variable Mutual Inductance Three Coil Transducer 120 4.6.5 Self Generating Type Inductive Transducers 121 4.6.6 Eddy Current Transducers 122 4.6.7 Magnetometer Search Coil 123 4.7 Capacitive Transducers 124 4.8 Piezoelectric Transducers 127 4.9 Photoelectric Effects 128 4.9.1 Photo Emissive 128 4.9.2 Photo Conductive Transducers 129 4.9.3 Photo Voltaic Cells 131 4.10 Hall Effect 131 4.11 Magnetostrictive Transducer 132 4.12 Ionization Transducers 133 4.13 Digital Displacement Transducers 133 Summary 135 Key Concepts 136 Review Questions 137 Multiple Choice Questions 138 Answers 140 Chapter 5 Measurement of Temperature 141 5.1 Introduction 146 5.2 Basic Concepts of Temperature 146 5.3 Measurement of Temperature 148 5.3.1 Temperature Measuring Instruments 149

(xv) 5.4 Measurement of Temperature by Changes in Physical Dimensions 152 5.4.1 Measurement of Temperature by Expansion of Solids 152 5.4.2 Measurement of Temperature by using Expansion of Liquids 155 5.5 Pressure Thermometers 157 5.6 Electrical Effects on Temperature 162 5.6.1 Thermo Resistive Elements 162 5.6.2 Fundamentals of Thermo Electricity 162 5.6.3 Laws of Thermo-Electric Power 165 5.7 Measurement of Temperature by Electrical Methods 166 5.7.1 Resistance Temperature Detector (RTD) or Electrical- Resistance Thermometers 166 5.7.2 Thermistors (Thermal Resistors) 170 5.7.3 Thermocouples 173 5.8 Semiconductor Junction Temperature Sensors 180 5.9 The Linear Quartz Thermometer 181 5.10 Thermometers using Changes in Emitted Thermal Radiation-Pyrometers 181 5.11 Types of Pyrometers 184 5.11.1 Total Radiation Pyrometer 184 5.11.2 Optical Pyrometer or Disappearing Filament Pyrometer or Monochromatic Brightness Radiation Thermometer 185 5.11.3 Infrared Pyrometer 187 5.12 Temperature Measurement by Changes in Chemical Phase 188 Summary 189 Key Concepts 190 Review Questions 192 Multiple Choice Questions 194 Answers 195 Chapter 6 Measurement of Pressure 197 6.1 Introduction 200 6.2 Definitions And Terminology 200 6.2.1 Atmospheric Pressure (P A ) 201 6.2.2 Absolute Pressure (P ABS ) 201 6.2.3 Gauge Pressure (P > P A ) 201 6.2.4 Vacuum Pressure (P A > P or P < P A ) 201 6.2.5 Relation between Absolute, Gauge, Atmospheric and Vacuum Pressure 201 6.2.6 Static Pressure 202 6.2.7 Total or Stagnation Pressure 202 6.2.8 Dynamic or Impact or Velocity Pressure 202 6.3 Classification of Pressure Measuring Devices 203 6.4 Dead Weight Tester 204

(xvi) Contents 6.5 Manometers 206 6.5.1 Piezometer 207 6.5.2 U-Tube Manometer 208 6.5.3 Single Column Manometer 210 6.5.4 U-Tube Differential Manometer 213 6.5.5 Inverted U-tube Differential Manometer 215 6.6 Mechanical Displacement Type Gauges 217 6.6.1 Ring Balance Manometer 217 6.6.2 Bell Type Pressure Gauges 218 6.7 Bourdon Tube Pressure Gauge 219 6.7.1 Tip Travel of Bourdon Tube 221 6.7.2 Errors and their Rectification (in Bourdon Tube) 222 6.7.3 Bourdon Tube Shapes and Configurations 222 6.8 Elastic Diaphragm Gauges 223 6.9 Bellows Gauges 226 6.10 Strain Gauge Pressure Cells 229 6.11 The McLeod Gauge 231 6.11.1 Formula for Errors 233 6.12 Thermal Conductivity Gauges 235 6.12.1 Pirani Gauge 235 6.12.2 Thermocouple Type Conductivity Gauge 237 6.12.3 Ionization Gauge 238 Summary 239 Key Concepts 239 Review Questions 241 Numerical Problems 243 Multiple Choice Questions 244 Answers 246 Chapter 7 Flow Measurement 247 7.1 Introduction 252 7.2 Nature of Flow 252 7.3 Classification of Flow Measurements 253 7.4 Primary or Quantity Methods 254 7.4.1 Tilting Trap Meter 254 7.4.2 Positive Displacement Meters 254 7.5 Flow (Obstruction) Meters 258 7.5.1 Venturi Meter 259 7.5.2 Orifice Meter or Orifice Plate 262 7.5.3 Flow-Nozzle Meter 265 7.5.4 Variable Area Meter or Rotameter 266 7.6 Turbine Meters 269 7.7 Magnetic Flow Meters 271 7.8 Vortex Shedding Flow Meters 272

(xvii) 7.9 Measurement of Fluid Velocities 273 7.9.1 Total - Pressure Probe (Pitot Static Tube) 273 7.9.2 Direction - Sensing Probes or Yaw-Angle Probe 275 7.10 Anemometers 276 7.10.1 Hot Wire Anemometers 276 7.10.2 Hot Film Anemometers 280 7.11 Measurement by Scattering 280 7.11.1 Laser Doppler Anemometry 281 7.12 Ultrasonic Anemometry 284 7.13 The Interferometer 284 7.13.1 The Schlieren 285 7.14 The Shadow Graph 286 7.15 Calibration of Flow Measuring Devices 286 7.16 Flow-Visualization Techniques 287 7.16.1 Dye Injection 288 7.16.2 Chemical Precipitates 288 7.16.3 Smoke Trails and Smoke Wire 288 7.16.4 Hydrogen Bubble Visualization 288 7.16.5 Laser Induced Fluorescence 288 Summary 289 Key Concepts 289 Review Questions 291 Multiple Choice Questions 293 Answers 295 Chapter 8 Measurement of Liquid Level 297 8.1 Introduction 301 8.2 Measurement of Liquid Level 301 8.3 Classification of Liquid-Level Measurement Methods 301 8.4 Direct Liquid Level Measurement Devices 302 8.4.1 Sight Glass Tube 302 8.5 Float Gauges 304 8.5.1 Float-Tape Liquid Level Gauges 304 8.5.2 Float Shaft Liquid Level Gauge 305 8.6 Indirect Liquid Level Measurement Devices 306 8.7 Hydrostatic Pressure Devices (Bubbler or Purge System) 307 8.7.1 Hydrostatic Pressure Devices for Open Tanks 308 8.7.2 Hydrostatic Pressure Devices for Closed Tanks: Bubbler or Purge System 309 8.8 Electric Liquid Level Sensors 311 8.8.1 Rheostat Operated by a Float 311 8.8.2 Capacitive Liquid Level Sensor 312 8.9 Gamma Ray Liquid Level Sensor 314 8.10 Ultrasonic Liquid Level Gauge 315

(xviii) Contents 8.11 Inductive Methods or Magnetic Level Indicator 316 8.12 Cryogenic Fuel Level Indicator 317 Summary 319 Key Concepts 319 Review Questions 320 Multiple Choice Questions 321 Answers 323 Chapter 9 Measurement of Speed 325 9.1 Introduction 329 9.2 Classification of Tachometers 329 9.3 Mechanical Tachometers 330 9.3.1 Revolution Counter and Timer 330 9.3.2 Tachoscope 331 9.3.3 Hand Speed Indicator (Modified Tachoscope) 331 9.3.4 Slipping Clutch Tachometer 332 9.3.5 Centrifugal Force Tachometer 333 9.3.6 Vibrating Reed Tachometer 333 9.4 Electrical Tachometers 335 9.4.1 Drag Cup Tachometers (Automobile Speedometers) 335 9.4.2 Commutated Capacitor Tachometer 336 9.4.3 Tacho Generators 337 9.4.4 Inductive Pick up Tachometer 340 9.4.5 Capacity Type Pick-up Tachometer 341 9.4.6 Photo Electric Tachometer 342 9.4.7 Stroboscope 343 Summary 346 Key Concepts 346 Review Questions 348 Multiple Choice Questions 349 Answers 352 Chapter 10 Measurement of Vibration and Acceleration 353 10.1 Introduction 356 10.2 Vibration Measurement 356 10.3 Transducers used in Vibration Measurement 357 10.3.1 Fixed Reference Type Transducer 357 10.3.2 Seismic Type Transducer 359 10.4 List of Transducers/Instruments used to Measure Vibration/Acceleration 360 10.4.1 Piezo Electric Accelerometer 361 10.4.2 Seismic Displacement Sensing Accelerometer 362 10.4.3 Strain - Gauge Accelerometer 363 10.4.4 Capacitance Vibration Sensor/Accelerometer 364

(xix) 10.4.5 Variable Induction Type Accelerometer 366 10.4.6 LVDT - Accelerometer 367 10.4.7 Reed Type Vibrometer 368 10.4.8 Vibration Measurement using Stroboscope 369 10.5 Factors Affecting the Choice of Transducers 370 10.6 Calibration of Vibration Transducers 371 10.7 Servo Accelerometer 371 10.8 Digital Accelerometer 374 Summary 376 Key Concepts 377 Review Questions 378 Multiple Choice Questions 379 Answers 381 Chapter 11 Measurement of Force, Torque and Power 383 11.1 Introduction 387 11.2 Methods of Measurement of Force 387 11.2.1 Direct Method 387 11.2.2 Indirect Method 388 11.3 Equal Arm Balance 388 11.4 Unequal Arm Balance 389 11.5 Pendulum Scale (Multi-Lever Type) 391 11.6 Elastic Force Meter (Proving Ring) 393 11.7 Strain Gauge Load Cell 393 11.8 Hydraulic Load Cell 395 11.9 Pneumatic Load Cells 396 11.10 Measurement of Torque and Power 397 11.10.1 Definitions of Torque and Power 398 11.10.2 Relation between Torque and Power 398 11.11 Dynamometers 399 11.11.1 Mechanical/Prony Brake Dynamometer 399 11.11.2 Hydraulic Dynamometer 400 11.11.3 Eddy Current Dynamometer 401 11.11.4 Electrical Generator Type 402 11.11.5 Driving Dynamometer 402 11.11.6 Transmission Dynamometer 402 11.12 Torsion Meter 406 11.12.1 Mechanical Torsion Meter 406 11.12.2 Optical Torsion Meter 407 11.12.3 Electrical Torsion Meters (Torque Measurement using Slotted Discs) 408 11.12.4 Strain Gauge Torsion Meter 409 (Strain Gauges on Rotating Shafts) 409

(xx) Contents Summary 411 Key Concepts 411 Review Questions 413 Multiple Choice Questions 415 Answers 416 Chapter 12 Strain and Stress Measurement 417 12.1 Introduction 420 12.2 Fundamentals of Stress and Strain 421 12.3 Strain Measurement 423 12.3.1 Positive Strain 423 12.3.2 Negative Strain 423 12.4 The Electrical Resistance Strain Gauge 424 12.4.1 The Metallic Resistance Strain Gauge 424 12.5 Types of Strain Gauges 427 12.5.1 Unbonded Strain Gauge 427 12.5.2 Bonded Strain Gauges 428 12.6 Selection and Preparation of Bonded Strain Gauge 432 12.6.1 Surface - Preparation and Mounting of Strain Gauges 432 12.6.2 Grid Materials 433 12.6.3 Backing, Base or Carrier Material 433 12.6.4 Bonding Materials or Cements (Adhesive) 434 12.6.5 Factors Affecting Selection of Bonded Metallic Strain Gauges 435 12.7 Temperature Compensation 435 12.8 Temperature Compensation using an Adjacent Arm Compensating Gauge 436 12.8.1 Self Temperature Compensation 439 12.9 Gauge Rosettes (Multiple Grids) 440 12.10 Wheatstone Bridge Circuit 447 12.10.1 One Active Strain Gauge (Quarter Bridge) or Tension Measurement using Strain Gauge 448 12.10.2 Two Active Strain Gauges (Half Bridge) or Tension and Compression Measuring Strain Gauges 449 12.11 Calibration 450 12.12 Applications of Strain Gauges 451 Summary 451 Key Concepts 452 Review Questions 454 Multiple Choice Questions 455 Answers 457 Chapter 13 Measurement of Viscosity and Surface Tension 459 13.1 Introduction 462 13.2 The Jargon of Viscosity 462

(xxi) 13.3 Classification of Viscometers 464 13.4 Capillary Tube Viscometer 465 13.5 Efflux Viscometers 466 13.5.1 Redwood Viscometer 466 13.5.2 Saybolt Viscometer 467 13.5.3 Engler Viscometer 468 13.6 Falling Sphere Viscometer 469 13.7 Rotating Cylinder Viscometers 471 13.7.1 Rotating Cylinder Viscometer (Concentric Cylinders Type) 471 13.7.2 Rotating Cylinder Electrical Viscometer 472 13.8 Surface Tension 473 13.9 Measurement of Surface Tension 475 13.9.1 Effects of Surface Tension 475 13.9.2 Methods of Measuring Surface Tension 476 13.9.3 Instruments used to Measure Surface Tension 476 13.10 Du Noüy Ring Tensiometer 477 13.11 Du Noüy-Padday Tensiometer 477 13.12 Wilhelmy Plate Tensiometer 478 13.13 Bubble Pressure Tensiometer 478 13.14 Goniometer/ Tensiometer 479 13.15 Some More Methods 479 13.15.1 Spinning Drop Method 479 13.15.2 Drop Volume Method 480 13.15.3 Capillary Rise Method 480 13.15.4 Stalagmometric Method 480 13.15.5 Sessile Drop Method 480 13.15.6 Vibrational Frequency of Levitated Drops Method 480 13.15.7 Resonant Oscillations of Spherical/ Hemispherical Liquid Drop Method 480 Summary 481 Key Concepts 482 Review Questions 484 Multiple Choice Questions 484 Answers 486 Chapter 14 Measurement of Humidity/ Dampness and Density/Specific Gravity 487 14.1 Introduction 491 14.2 Terminology 491 14.3 List of Instruments used to Measure Humidity 492 14.4 Psychrometers (Wet and Dry Bulb Thermometers) 493 14.5 Sling Psychrometer 493

(xxii) Contents 14.6 Absorption Hygrometers 495 14.6.1 Mechanical Humidity Sensing Absorption Hygrometer 495 14.6.2 Electrical Humidity Sensing Absorption Hygrometer 497 14.7 Dew Point Meter 498 14.8 Fundamentals of Density and Specific Gravity 500 14.9 Instruments to Measure Specific Gravity and Density 501 14.10 Pycnometer 501 14.11 Hydrometers 503 14.11.1 Simple Hydrometer 503 14.11.2 Photo-Electric Hydrometer 504 14.12 Differential Type Bubbler Systems 506 14.12.1 Differential Type Bubbler System with Two Vessels Attached by a Manometer and Reference Column Method 506 14.12.2 Differential Type Bubbler System with Single Vessel Attached and Pressure Gauge 507 14.13 Special Applications of Hydrometers 508 Summary 509 Key Concepts 509 Review Questions 511 Multiple Choice Questions 512 Answers 514 Chapter 15 Elements of Control Systems 515 15.1 Introduction 518 15.2 Basic Components of a Control System 518 15.3 Control Systems Terminology 518 15.4 Types of Control Systems 521 15.4.1 Open Loop Control Systems (Non- Feedback Systems) 521 15.4.2 Closed Loop or Feedback Control Systems 523 15.4.3 Advantages of Feedback Control Systems 524 15.4.4 Positive and Negative Feedback 528 15.5 Differences between Open Loop and Closed Loop Systems 531 15.6 Servo Mechanism 532 15.7 Requirements of a Control System 534 15.7.1 Stability 534 15.7.2 Accuracy 534 15.7.3 Speed of Response 534 15.8 Control Systems Case Studies 534 15.8.1 Speed Control System in Automobiles 535 15.8.2 Speed Control System in IC Engines 537 15.8.3 Temperature Control System of the Passenger Compartment of a Car 538 15.8.4 Automatic Tank-Level Control System 540

(xxiii) Appendix 549 Index 563 15.8.5 Liquid Level Control System (Automatic and Manual) 540 15.8.6 Feedback System in Nature Biological System 541 15.8.7 Position Control System Missile Launching and Guidance System 542 Summary 543 Key Concepts 544 Review Questions 545 Multiple Choice Questions 547 Answers 548