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Introduction to Temperature Measurement

Bangladesh BEST programme. Introduction to Temperature Measurement. Nihal Gunasekara Sri Lanka. Temperature and Scale. Bangladesh BEST Programme. What is temperature ? The first thermometer Types of scale Classification of thermometer International Temperature Scale. A. B.

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Introduction to Temperature Measurement

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  1. Bangladesh BEST programme Introduction to Temperature Measurement NihalGunasekara Sri Lanka

  2. Temperature and Scale Bangladesh BEST Programme • What is temperature ? • The first thermometer • Types of scale • Classification of thermometer • International Temperature Scale

  3. A B C Thermal equilibrium What is temperature ? Bangladesh BEST Programme • Ruler for the cool and hot ? • Motivation of the thermometer development • The zeroth law of thermodynamics • Temperature means the level of thermal energy. • Driving force for the heat flow

  4. The first thermometer Bangladesh BEST Programme • In 1594, G. Galileo • A type of gas thermometer • Volume change with temperature

  5. Bangladesh BEST Programme The First Glass Thermometer • In 1654,Ferdinand II, Grand Duke of Tuscany

  6. Bangladesh BEST Programme History of Thermometry • The first mercury thermometer • In 1706, Netherlands, Fahrenheit • The first platinum resistance thermometer • In late 19th century, Callendar • The first commercial thermocouple • In 1885, Le Chatelier,Type S

  7. Types of Scale Bangladesh BEST Programme • Fahrenheit (oF) • In 1706, Netherlands,Fahrenheit • In Europe, coldest day : 0 oF (= - 17.8 oC) • Hottest day : 100 oF(= 37.8 oC) • 0 oC = 32 oF • 100 oC = 212 oF oF = 9/5 oC + 32

  8. Bangladesh BEST Programme Defining Temperature Scale • degree Celsius (oC) • In 1742, Sweden - A. Celsius • Ice point : 0 oC • Water boiling point : 100 oC • Divided into 100 parts • Currently used together with international unit

  9. Bangladesh BEST Programme Absolute temperature - K (thermodynamic temperature) • In 1848, Lord Kelvin • The second law of thermodynamics and Carnot heat engine • K = oC + 273.15 • International unit of temperature scale

  10. Bangladesh BEST Programme • History of International Temperature Scale • 1927, The International Temperature Scale of 1927 (ITS-27) • 1948, The ITS-48 • 1960, Amended edition of the ITS-48 • 1968, The International Practical Temperature Scale of 1968 (IPTS-68) • 1976, Amended edition of the IPTS-68 • 1990, The ITS-90

  11. Bangladesh BEST programme International Temperature Scale of 1990

  12. Bangladesh BEST Programme • Triple Point of Water • Distilled water • De-ionized water • Air-free state • Water + Vapor + Ice • Reference of scale

  13. Equilibrium State Bangladesh BEST programme

  14. Bangladesh BEST Programme Metal Fixed-Point

  15. Bangladesh BEST Programme Fixed-points Below 273.16 K

  16. Bangladesh BEST Programme Fixed-points Above 273.16 K

  17. Bangladesh BEST Programme Defining Fixed Points of ITS -90

  18. Different Types of Thermometers Bangladesh BEST Programme • Thermocouple thermometers • Resistance thermometers • Liquid-in-glass thermometers • Bimetallic thermometers • Radiation thermometers • Optical pyrometers

  19. A emf Cold Hot Cold B Thermoelectric theory(Seebeck effect) Bangladesh BEST Programme • In 1821, T.J.Seebeck found A and B are two different metallic wires.

  20. Bangladesh BEST Programme Practical Usage Thermocouple wires Extension wires Measuring point Measuring Instrument Reference junctions

  21. Reference (cold ) Junction Bangladesh BEST Programme • Accurate Measurements Ice Bath • Modern TC Thermometers Compensation incorporated • C J at a Constant Temp. Isothermal Block

  22. Bangladesh BEST Programme Types and Materials

  23. Resistance Thermometers Bangladesh BEST Programme • Platinum Resistance Thermometers (PRT) • Standard Platinum Resistance Thermometers (SPRT) • High Temperature Platinum Resistance Thermometers (HTPRT)

  24. Resistance Thermometers Bangladesh BEST Programme • PRT Pt-100 100 Ω at 0 °C Working Standard • SPRT 25 Ω at 0 °C Reference Standard • HTPRT 2.5 Ω at 0 °C Reference Standard • Available in the Range - 200 °C to 1000 °C

  25. Principle of Operation Bangladesh BEST Programme • Change in Temperature of a Resistive Element Resistance Value Changed Platinum Element

  26. Terminal Configuration Bangladesh BEST Programme Red White Red Red White Pt -100/2 Pt – 100/3 Red Red White White Pt- 100/4

  27. Bangladesh BEST Programme Resistance Thermometers Construction PRT-100 Thin Film PRT Reference SPRT Long stem SPRT

  28. Liquid in Glass Thermometers Bangladesh BEST Programme • Principle of Operation : Expansion of Liquid in a Glass Capillary Tube to Sense the Temperature • Measuring Range : -20 °C to 600 °C

  29. Liquid in Glass Thermometers Bangladesh BEST Programme Condition of Immersion • Total Immersion Thermometers • Partial Immersion Thermometers • Complete Immersion Thermometers Measuring Range : -20 °C to 600 °C

  30. Liquid in Glass Thermometers Bangladesh BEST Programme

  31. BimetallicThermometers Bangladesh BEST Programme • Principle of Operation : Difference in the Thermal Expansion of Two Metals • Measuring Range : -100 °C to 540 °C • Accuracy : about 1% of reading

  32. BimetallicThermometers Bangladesh BEST Programme

  33. Radiation Thermometers Bangladesh BEST Programme • Principle of Operation : As the temperature of the object increases more energy is emitted at progressively shorter wavelengths • Measuring Range : 600 °C to 3500 °C • Detectors : Mostly Silicon or Germanium

  34. Relationship Between Wavelength of the Emitted Radiation and Spectral Radiance Bangladesh BEST Programme

  35. Optical Pyrometers Bangladesh BEST Programme • Disappearing filament type • Constant radiation disappearing filament type • Automatic optical type

  36. Disappearing Filament Type Pyrometer Bangladesh BEST Programme

  37. Constant Radiation Disappearing Filament Type Pyrometer Bangladesh BEST Programe

  38. Bangladesh BEST Programme Thank You

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