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Industrial Instrumentation

Industrial Instrumentation. Dr. –Ing. Naveed Ramzan. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 1. Home work-1.

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Industrial Instrumentation

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  1. Industrial Instrumentation Dr. –Ing. Naveed Ramzan PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 1

  2. Home work-1 PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 2

  3. Home work-1 PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 3

  4. “It is time to turn up the heat but first you must learn how to measure it” Temperature Sensor PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 4

  5. Relative Scales Fahrenheit (°F) Celsius (°C) Absolute Scales Rankine (°R) Kelvin (K) Temperature Measurement Scales

  6. Temperature Measurement Scales Imperial Fahrenheit (⁰F) / Rankine (⁰R) +/- 460 Metric Celsius (⁰C) / Kelvin (⁰K) +/- 273 212⁰F 672⁰R 373⁰K 100⁰C Fahrenheit [°F] = [°C] · 9/5 + 32 Celsius [°C] = ([°F] − 32) · 5/9 Kelvin [K] = [°C] + 273.15 Rankine [°R] = [°F] + 459.67 0⁰C 273⁰K 32⁰F 492⁰R -18⁰C 255⁰K 0⁰F 460⁰R -273⁰C 0⁰K 0⁰R -460⁰F

  7. (°F) = 9/5*(°C) +32 (°C) = 5/9*[(°F) –32] (°F) = (°R) – 459.67 (°C) = (K) – 273.15 Relationship of Temperature Measurement Scales

  8. Methods of Temperature Measurement • Mechanical Methods • Electrical Methods PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 8

  9. Methods of Temperature Measurement • Thermocouples • Thermistors • Electrical resistance change (RTD) • Pyrometers • Expansion of materials PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 9

  10. Seebeck Effect: The generation of current in a circuit comprising of two wires of dissimilar metals in the presence of temperature difference Thermocouples When 2 dissimilar metals are joined together to form a junction, an emf is produced which is proportional to the temperature being sensed. The magnitude of emf depends on the junction temperature. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 10

  11. Thermocouples PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 11

  12. Typical Industrial Thermocouple Assembly PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 12

  13. TCs are identified by a single letter type and grouped according to their temperature range Base Metals – up to 1000 °C Type J, Type E, Type T, Type K Noble Metals – up to 2000 °C Type R, Type S, Type B Refractory Metals – up to 2600 °C Type C, Type D, Type G Thermocouple Types PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 13

  14. Metal Combinations Chromel = Nickel-chromium Alumel = Nickel-aluminum Constantan = Copper-nickel PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 14

  15. Thermocouple Tables Voltage to Temperature Conversion 1.445 mV equal to temperature …………………………………….. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 15

  16. Thermocouple Callibration Charts Voltage to Temperature Conversion PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 16

  17. Thermistors • Thermistor, a word formed by combining thermal with resistor, is a temperature-sensitive resistor fabricated from semiconducting materials. • The resistance of thermistors decreases proportionally with increases in temperature. • The operating range can be -200°C to + 1000°C PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 17

  18. Thermistors • The thermistors can be in the shape of a rod, bead or disc. • Manufactured from oxides of nickel, manganese, iron, cobalt, magnesium, titanium and other metals. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 18

  19. Thermistors • The word that best describes the thermistors is “sensitive” PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 19

  20. Thermistor Charts Resistance to Temperature Conversion PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 20

  21. Advantages: Small sizes and fast response Low cost Suitability for narrow spans Disadvantages: More susceptible to permanent decalibration at high temperatures. Use is limited to a few hundred degrees Celsius. Respond quickly to temperature changes, thus, especially susceptible to self-heating errors. Very fragile Thermistors PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 21

  22. Electrical Resistance Change (RTD) Resistance Temperature Detector- RTD The industry standard is the platinum wire RTD (Pt100) whose base resistance is exactly 100.00 ohms at 0.0 °C. RTD (Resistance Temperature Detector) is a temperature sensitive resistor. It is a positive temperature coefficient device, which means that the resistance increases with temperature. The resistive property of the metal is called its resistivity. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 22

  23. Electrical Resistance Change (RTD) Platinum Wire RTDs (PRTs) PRTs have established themselves as the de-facto industry standard for temperature measurement, and for many reasons: • linear temperature sensors • Resistance vs temperature characteristics are stable and reproducible • linear positive temperature coefficient (-200 to 800 °C) • very accurate and suitable for use as a secondary standard PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 23

  24. Electrical Resistance Change (RTD) Platinum Scale ( 0 to 100 °C ) PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 24

  25. Electrical Resistance Change (RTD) International Practical scale for Temperature (0 to 650. 30 °C) PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 25

  26. Electrical Resistance Change (RTD) International Practical scale for Temperature (Below 0 °C) PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 26

  27. Electrical Resistance Change (RTD) International Practical scale for Temperature PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 27

  28. 10 ohms Copper RTD - .00427 coefficients 100 ohms Platinum RTD - .00385 coefficients (new IEC) 100 ohms Platinum RTD - .00392 coefficients (old) 120 ohms Nickel RTD - .00672 coefficient 604 ohms Nickel-Iron RTD - .00518 coefficients Electrical Resistance Change (RTD) Other RTDs All base resistances are specified at a temperature of 0 degrees C A Pt1000 will have a base resistance of 1000 ohms at 0 deg. C PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 28

  29. RTDs with a bridge circuit Only practical if the RTD lead wires are short. In many applications the RTD is located far from the conditioning circuit adding extra resistance because the length of the copper lead wire. Cu = 0.0302 Ω per ft. How much error will 100 ft length of Cu lead wire introduce? Most RTD’s have an extra wire to compensate for the length of lead wire. PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 29

  30. Not standardized but this is common colour arrangement. Some (like in the lab) will use BLK-BLK-RED RTD Colour Code PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 30

  31. Pyrometry is a technique for measuring temperature without physical contact An apparatus for measuring high temperatures that uses the radiation emitted by a hot body as a basis for measurement. Radiation pyrometers ( measurement of radiant energy) Optical Pyrometers (comparison of the intensities ) Pyrometer PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 31

  32. Radiation pyrometers Radiation Pyrometer PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 32

  33. Optical pyrometers (600 to 3000 °C) Radiation Pyrometer • basic principle of using the human eye to match the brightness of the hot object to the brightness of a calibrated lamp filament inside the instrument • Compare incident radiation to internal filament radiation PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 33

  34. Bimetallic Thermometer (Expansion of solids) Expansion Thermometers Effect of unequal expansion of a bimetallic strip • Different metals have difference coefficient. • Configured as spiral or helix for compactness • - Can be used with a pointer to make an inexpensive compact rugged thermometer. Bimetallic thermometer PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 34

  35. Bimetallic Thermometer (Expansion of solids) Expansion Thermometers PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 35

  36. Bimetallic Thermometer (Expansion of solids) Expansion Thermometers Thermal expansion methods: Bimetallic sensors PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 36

  37. Filled Thermal Systems (Filled System Thermometer, Filled Bulb Thermometer) Expansion Thermometers Spiral Type Bourdon Tube • Similar operation as the liquid in glass • Bulb • Capillary tube • Pressure element • Scale PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 37

  38. Filled Thermal System Classes (Filled System Thermometer, Filled Bulb Thermometer) Expansion Thermometers • Class l A,B – Liquid filled • Class ll A,B,C,D –Vapour filled • Class lll A,B – Gas filled • Class V A,B – Mercury Filled PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 38

  39. Filled Thermal System Classes (Filled System Thermometer, Filled Bulb Thermometer) Expansion Thermometers • Temperature Range Response • Class l: -125 F to + 600 F Slowest • Class ll: -40 to 32 or 32 to 600 F Fastest • Class lll: -450 F to +1400 F Fast • Class V: -40 F to +1200 F Fast PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 39

  40. Data Required to Provide Measurement of Process Temperature PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 40

  41. Data Required to Provide Measurement of Process Temperature PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 41

  42. Data Required to Provide Measurement of Process Temperature PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 42

  43. Data Required to Provide Measurement of Process Temperature PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 43

  44. Criteria for Selecting a Suitable Temperature Measuring Instrument PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 44

  45. Summary of Temperature Sensor Characteristics PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 45

  46. Summary of Temperature Sensor Characteristics PEC – UET Lahore Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 46

  47. Discussion & Questions? Dr. Shahid Naveed 1. April 2014 / Dr. –Ing Naveed Ramzan 47

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