1 THE CONCEPT OF TEMPERATURE

Transcription

1 1 THE CONCEPT OF TEMPERATURE Historical Perspective, Early Definitions of Temperature, A Simple Qualitative Definition of Temperature, Units of Temperature for Various Temperature Scales, Conversion between Temperature Scales, The Thermal Expansion of Gases, Absolute Zero by the Gas Thermometer, Pressure-Temperature Relationships, The Perfect Gas Law, Gas Thermometry, High-Temperature Gas Thermometry, Summary, 18 References, 19 2 THE THERMODYNAMIC TEMPERATURE SCALE 2.1 Thermodynamic Terms Defined, The Carnot Cycle, Analysis.of the Carnot Cycle, The Kelvin Thermodynamic Temperature Scale, Fundamental Temperature Scales, 32 References,34 Recommended Reading, ix

2 x Problems, 35 Answers ENTROPY, TEMPERATURE AND STATISTICAL MECHANICS -3.1 The Concept of Entropy, 39 ~3.2 Entropy as an Exact Differential, Reciprocal Temperature as an Integrating Factor in Two Variables, Reciprocal Temperature as an Integrating Factor with More Than Two Variables, Qualitative Relations between Macro Concepts and Micro Concepts for Entropy, Background for the Quantitative Relationship of Microscopic to Macroscopic Thermodynamics, Basic Statistical Mechanic Premises, Entropy from a Statistical Mechanic Viewpoint, Temperature from a Statistical Mechanic Viewpoint, Energy Exchange between Two Bodies, 54 References THE INTERNATIONAL PRACTICAL TEMPERATURE SCALE Historical Background, Basis for the International Practical Temperature Scale, Evolution of the International Practical Temperature Scale, The IPTS-68 as Amended, EPT -76: A Provisional Scale of IPTS, The Relationship of IPTS-68 to Thermodynamic Temperatures, The International Temperature Scale of 1990, International Measurement Confederation, 96 References GENERAL CHARACTERISTICS OF TEMPERATURE MEASURING DEVICES AND TREATMENT OF DATA 5.1 Desirab.le Characteristics of Temperature Measuring Devices, Actual Characteristics of Temperature Measuring.Devices, The Reduction of Data: Curve Fitting, Curve Fitting for Temperature Measurement Functions, 104 Reference,,- lon 99

3 rnnti=nt~ xi Problems, 106 A n~wp.r~ LIQUID -IN-GLASS THERMOMETERS Historical Perspective, Thermometer Nomenclature, Types of Immersion, Thermometer Construction, Techniques for Using Liquid-in-Glass Thermometers, 119 References, 123 Problems, 124 A n!:wpr!: 1?4 7 SEALED LIQUID OR GAS SENSING INSTRUMENTS AND BIMET ALLIC SENSORS Gas Pressure Thermometers, Liquid-Filled Pressure Sensors, Remote Thermometers., Vapor Pressure Thermometers, Bimetallic Temperature Sensing Devices, 133 References, 138 Problems, 138 An!;wers ELECTRICAL RESIST ANCE TEMPERATURE MEASUREMENT USING MET ALLIC SENSORS Historical Perspective, Resistance of Sensing Elements, Platinum Resistor Sensitivity, Origin of the Callendar Equation, Sensing Element Construction, The Connecting Wires, Principles of Electrical Resistance Measureme~1, Resistance Measuring Instruments Requirements, Ohm's Law Devices, Bridge Measuring Instruments, Out-of-Balance Bridges, Alternating-Current Bridges, Compensation for Sensor Nonlinearity, T..te Interpolating Equations, 191 References, 197 Problems, 199 A...""'I'.." ")00

4 xii 9 THERMISTORS AND SEMICONDUCTORS FOR TEMPERATURE MEASUREMENT 9.1 Introduction, The Thermistor as a Semiconductor, Modification of the Resistance- Temperature ~.Relationship, Wheatstone Bridge Thermistor Circuit, Analog Output Thermistor Circuits, Digital Output Thermistor Circuits, Germanium Resistance Thermometers, Junction Semiconductor Devices, 230 References, THERMOELECTRIC TEMPERATURE MEASUREMENT 10.1 Historical Perspective, Theory of Thermoelectricity, The Concept of Absolute Thermoelectric Power, Electronic Specific Heat, Commercial Thermocouple Compositions, The Seebeck Voltage-Temperature Relationship, Absolute Thermoelectric Power of Commercial Thermocouple Alloys, Practical Thermocouple Laws, Analysis of Thermoelectric Potentials, The Importance of Temperature Gradients, The Connecting Wires, Methods of Making Thermocouple Junctions, Thermocouple Insulation, Thermocouple Protection, Deterioration of Thermocouples, Thermoelectric Voltage Measurements, Reference Junctions, Special Thermocouple Circuits, 302 References, 304 Problems, 305 Answers, THEORY OF RADIANT HEAT TRANSFER AS A BASIS FOR TEMPERATURE MEASUREMENT BY RADIANT TECHNIQUES 11.1 Introduction, i Kirchhoff's Law of Optics, Reflectance and Reflectivity, Transmittance or Transmissivitv, 317

5 xiii 11.5 Absorbance or Absorptivity, The Concept of a Blackbody, The Blackbody as a Perfect Emitter, Emit~ance and Absorbance of a Blackbody, Emittance from Real Bodies: Blackbody Cor\ditions, Definitions and Nomeliclature for Blackbody Radiation, Planck's Law of Blackbody Radiation, Wien's Law of Blackbody Radiation, Deviations from Blackbody Conditions, Emittance and Emissivity Defined, !5 Gray Body, ~ The Stefan-Boltzmann Law, Blackbody Radiation within Wavelength Intervals, Blackbody Radiation Sources, Tungsten Strip Lamps, Absolute Intensity Measurements, Relative Intensity Measurements, The Concept of a Brightness Temperature, Segmented Disks, Filters or Absorbing Screens: Pyrometer Brown Glass Filter, Summary, 350 References, THE DISAPPEARING FILAMENT OPTICAL PVROMETER Introduction, Accuracyof Measurement, Leeds and Northrup 8630 Optical Pyrometer, The Effective Wavelength of Pyrometer Red Filters, 359 J2.5 Small Target Optical Pyrometers, The Pyro Optical Pyrometer, Effect of Emittance Errors, Practical Applications Pyrometers, 367 of Disappearing Filament Optical, 12.9 Two-Color Pyrometers, 370 References, 371 Problems, 371 Answers, 372

6 xiv 13 PHOTOELECTRIC OPTICAL PYROMETERS {AUTOMATIC AND INFRARED) 13.1 Introduction, ,2. Basic Elements of Photoelectric Temperature Measurement, ,~ ' The Optical S.ystem, ,4 Optical Filters, ,5 Photoelectric Detectors, Solid-State Photodiode Detectors, , 7 Photomultiplier Detectors, ,8 Thermal Detectors, ,9 Bolometers, Thermopile Detectors, ,11 Infrared Sighting Systems, ,12 Examples of Commercial Infrared Pyrometers, ,13 Summary, 407 References TOTAL RADIATION PYROMETERS 14.1 Introduction, The Stefan-Boltzmann Law for Total Radiation Pyrometers, Geometry of Optical Systems without Lenses or Mirrors, Geometryof Lens Systems for Total Radiation Pyrometry, Geometry of Mirror Optic Systems for Total Radiation Pyrometers, Sapphire Light Guide Total Radiation Pyrometers, The Intensity of Radiation Reaching the Sensor, Sensor Temperature Response, Electrical Shunt Compensation, Thermal Shunt Compensation, Output Characteristics, Target Tubes and Sighting Tubes, Auxiliary Windows, Emittance Corrections, Ambient'Temperature, Linearizing Circuitry, 435 References, NOVEL METHODS OF TEMPERATURE MEASUREMENT Introduction, Phosphor Quenching (Thermographic Phosphors), 436

7 xv 15.3 Fluoroptic Temperature Measurement, Piezoelectric Resonant Frequency, Thermal Noise, Thermaf Imaging, Infrared Photography, Sp~ctroscopic Temperature Measurements, Index of Refraction Methods, Temperature Sensitive Indicators (Crayons, Paints, Transfers), Liquid Crystal Sensors, Ultrasonic Thermometry, Microwave Radiometry, Acoustic Thermometry, 451 References, PYROMETRIC CONES 16.1 Introduction, Historical Perspective, Orton Pyrometric Cones, Pyrometric Cone Pe.rformance, Pyrometric Cone Setting Procedures, Determination of Pyrometric Cone Equivalence, 464 References, CALIBRATION METHODS 17.1 Introduction, Classification of Standardization Methods, Thermodynamic Basis for Primary Standards, Calibration Errors, Cumulation of Uncertainty, Constant Temperature Zones, ? Immersion Errors, Calibration in a Test Facility ver~us Calibration in Situ, The Triple Point of Water, O Cryogenic Triple Points, The Ice Point, The Triple point of Gallium, The Melting Point of Gallium, Freezing Points of Tin, Lead, Zinc, Antimony, Aluminum, Silver, and Gold, Const-ant Temperature Sources, Comparison Furnaces, Heat Pipes,

8 xvi Low- Temperature Blackbody Sources, High- Temperature Blackbody Sources, National Bureau of Standards Calibration Services and Standard Reference Materials, Brightness Temperature Sources, 490 ~ 7.22,, Electrical Detection of Melting Points Using a Wire Bridge or Optical Pyrometer, Liquid-in-Glass Thermometer Calibration, 491 References INSTALLATION EFFECTS 18.1 Introduction, The Purpose of a Temperature Measurement, Thermal Mass, Immersion Errors (Insertion Errors), Insulated Wire Model, Errors from Radiant Heat Transfer, Radiation Methods of Measurement, Temperatures of Rapidly M.oving Fluids, Surface Temperature Measurement, Consumable Thermocouples, Shielding from Thermal Radiation, High- Temperature Gases, Summary, 502 References, DYNAMIC RESPONSE OF SENSORS 19.1 Introduction, Convection Cooling a Rodlike Sensor, Sensors in Enclosures, Response to a Ramp Change, Reducing Thermal Lag Time, Determining Sensor Time Constants, Calculation of Thermocouple Time Constants, References TEMPERATURE INSTRUMENTATION AND CONTROL 20.1 Introduction, The Feedback Loop, A Typical Control Situation, Temperature Controllers, Control Action, Analog versus Digital Concepts, Levels of Comrnlt~r rnntrnl ""a 518

9 20.8 Control Element and Computer Environments, Data Acquisition and Conversion, Signal Processing, Filt~ring, Signal Transmitting, SoJtr.ces of Noise, Amplifiers, Microprocessor-Controlled Instruments, Microcomputer-Controlled Instruments, Summary, 534 Recommended Reading, 534 APPENDIX THERMOCOUPLE REFERENCE TABLES INDEX