Lecture Sensors and analytical devices: Temperature measurement - Nguyễn Công Phương

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Lecture Sensors and analytical devices: Temperature measurement include all of the following: Thermoelectric effect sensors (thermocouples), varying resistance devices, semiconductor devices, radiation thermometers, thermography (thermal imaging), thermal expansion methods, quartz thermometers, fiber – optic temperature sensors,...

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Nội dung Text: Lecture Sensors and analytical devices: Temperature measurement - Nguyễn Công Phương

Nguyễn Công Phương Sensors and Analytical Devices Some Basic Measurement Methods, Temperature Measurement
Contents A. Introduction B. Sensors Characteristics C. Some Basic Measurement Methods D. Measurement Systems sites.google.com/site/ncpdhbkhn 2
Some Basic Measurement Methods I. Sensor Technologies II. Temperature Measurement III. Pressure Measurement IV.Flow Measurement V. Level Measurement VI.Mass, Force, and Torque Measurement VII.Translational Motion, Vibration, and Shock Measurement VIII.Rotational Motion Transducers sites.google.com/site/ncpdhbkhn 3
Temperature Measurement 1. Introduction 2. Thermoelectric Effect Sensors (Thermocouples) 3. Varying Resistance Devices 4. Semiconductor Devices 5. Radiation Thermometers 6. Thermography (Thermal Imaging) 7. Thermal Expansion Methods 8. Quartz Thermometers 9. Fiber – Optic Temperature Sensors 10. Color Indicators 11. Change of State of Materials 12. Choice between Temperature Transducers sites.google.com/site/ncpdhbkhn 4
Introduction • Temperature measurement is very important in all aspects of life. • In engineering applications, it is the most commonly measured process variable. • Difficulty: any given temperature cannot be related to a fundamental standard of temperature. • 10 classes of instrument based on 10 principles: – Thermoelectric effect – Resistance change – Sensitivity of semiconductor device – Radiative heat emission – Thermography – Thermal expansion – Resonant frequency change – Sensitivity of fiber-optic devices – Color change – Change of state of materials sites.google.com/site/ncpdhbkhn 5
Temperature Measurement 1. Introduction 2. Thermoelectric Effect Sensors (Thermocouples) 3. Varying Resistance Devices 4. Semiconductor Devices 5. Radiation Thermometers 6. Thermography (Thermal Imaging) 7. Thermal Expansion Methods 8. Quartz Thermometers 9. Fiber – Optic Temperature Sensors 10. Color Indicators 11. Change of State of Materials 12. Choice between Temperature Transducers sites.google.com/site/ncpdhbkhn 6
Thermoelectric Effect Sensors (1)  E  Metal 1 Metal 2 E  a1T  a2T 2  a3T 3  ...  anT n  a1T Thermocouples sites.google.com/site/ncpdhbkhn 7
Thermoelectric Effect Sensors (2) E1 Th E2 E1 Th E3 E2 E4 E1 Th E3 E5 sites.google.com/site/ncpdhbkhn 8
Thermoelectric Effect Sensors (3) Em  E1  E2  E3  E4  E5 E2 E4 Em E1 Th  E1  Em  E2  E3  E4  E5 E3 E5 http://www.pcbheaven.com/wikipages /How_Thermocouples_Work/?p=1  E1  Em sites.google.com/site/ncpdhbkhn 9
Thermoelectric Effect Sensors (4) • Chromel – constantan (type E) – Highest measurement sensitivity: 68 μV/oC – Inaccuracy: ±0.5% – Range: –200oC up to 900oC • Iron – constantan (type J) – Sensitivity: 55 μV/oC – Inaccuracy: ±0.75% – Range: –40oC up to 750oC • Copper – constantan (type T) – Sensitivity: 43 μV/oC – Inaccuracy: ±0.75% – Range: –200oC up to 350oC sites.google.com/site/ncpdhbkhn 10
Thermoelectric Effect Sensors (5) • Chromel – alumel (type K) – Highest measurement sensitivity: 41 μV/oC – Inaccuracy: ±0.75% – Range: –200oC up to 1300oC – Applications: 700oC up to 1200oC – Widely used, general – purpose • Nicrosil – nisil (type N) – Sensitivity: 39 μV/oC – Inaccuracy: ±0.75% – Range: up to 1300oC – Long – term stability & life • Nickel/molybdenum – nickel – cobalt – One wire made from a nickel – molybdenum alloy with 18% molybdenum & the other wire made from a nickel – cobalt alloy with 0.8% cobalt – Range: up to 1400oC – Rarely used except for special applications such as temperatuer measurement in vacuucm furnaces sites.google.com/site/ncpdhbkhn 11
Thermoelectric Effect Sensors (6) • Chromel – alumel (type K) – Sensitivity: 41 μV/oC – Inaccuracy: ±0.75% – Range: –200oC up to 1300oC – Applications: 700oC up to 1200oC – Widely used, general – purpose • Nicrosil – nisil (type N) – Sensitivity: 39 μV/oC – Inaccuracy: ±0.75% – Range: up to 1300oC – Long – term stability & life • Nickel/molybdenum – nickel – cobalt (type M) – One wire made from a nickel – molybdenum alloy with 18% molybdenum & the other wire made from a nickel – cobalt alloy with 0.8% cobalt – Range: up to 1400oC – Rarely used except for special applications such as temperatuer measurement in vacuucm furnaces sites.google.com/site/ncpdhbkhn 12
Thermoelectric Effect Sensors (7) • Platinum (type B) – One wire made from a platinum – rhodium alloy with 30% rhodium & the other wire made from a platinum – rhodium alloy with 6% rhodium – Sensitivity: 10 μV/oC – Range: 50oC up to 1800oC • Platinum (type R) – One wire made from pure platinum & the other wire made from a platinum – rhodium alloy with 13% rhodium – Sensitivity: 10 μV/oC – Inaccuracy: ±0.5% – Range: 0 up to 1700oC • Platinum (type S) – One wire made from pure platinum & the other wire made from a platinum – rhodium alloy with 10% rhodium – Sensitivity: 10 μV/oC – Inaccuracy: ±0.5% – Range: 0 up to 1750oC • Tungsten (type C) – One wire made from pure tungsten & the other wire made from a tungsten/rhenium alloy – Sensitivity: 20 μV/oC – Range: 0 up to 2300oC • Chromel – gold/iron – One wire made from chromel & the other wire made from a gold/iron alloy – Sensitivity: 15 μV/oK – Range: from 1.2oK – For very low temperature applications sites.google.com/site/ncpdhbkhn 13
Thermoelectric Effect Sensors (8) • Manufactured by connecting together two wires of different materials – Welding (the most common technique), or – Soldering, or – Twisting the wire ends together • Diameter – Between 0.4 & 2 mm (usually) – Some special case: 0.1 μm (for fast response time) sites.google.com/site/ncpdhbkhn 14
Temperature Measurement 1. Introduction 2. Thermoelectric Effect Sensors (Thermocouples) 3. Varying Resistance Devices 4. Semiconductor Devices 5. Radiation Thermometers 6. Thermography (Thermal Imaging) 7. Thermal Expansion Methods 8. Quartz Thermometers 9. Fiber – Optic Temperature Sensors 10. Color Indicators 11. Change of State of Materials 12. Choice between Temperature Transducers sites.google.com/site/ncpdhbkhn 15
Varying Resistance Devices • Rely on the physical principle of the variation of resistance with temperature. • 2 types: resistance thermometers & thermistors. sites.google.com/site/ncpdhbkhn 16
Varying Resistance Devices, Resistance Thermometers (1) • A.k.a. resistance temperature devices. • R = R0(1 + a1T + a2T2 + ... + anTn) • R ≈ R0(1 + a1T) • Platinum: – The most linear characteristic & the most commonly used. – Inaccuracy: ±1.2%. – Very expensive • Platinum thermometers are made in 3 forms: – A film deposited on a ceramic substrate. – A coil mounted inside a glass or ceramic probe. – A coil wound on a mandrel sites.google.com/site/ncpdhbkhn 17
Varying Resistance Devices, Resistance Thermometers (2) • The nominal resistance (platinum) at 0oC is typically 100 or 1000Ω. • Sensitivity (platinum): – 0.385Ω/oC (100Ω type) – 3.85Ω/oC (1000Ω type) • The working range: – Platinum: –270 to 1000oC – Copper: –200 to 260oC – Nickel: –200 to 430oC – tungsten: –270 to 1100oC sites.google.com/site/ncpdhbkhn 18
Varying Resistance Devices, Thermistors • Made from beads of semiconductor material prepared from oxides of the iron group of metals (chromium, cobalt, iron, manganese, & nickel). • Have a negative temperature coeficient, that is, resistance decreases as temperature increases: R  R0e  (1/ T 1/ T0 ) • Disadvantages: – Nonlinear – Low sensitivity • Advantages: – Low cost – Small size sites.google.com/site/ncpdhbkhn 19
Temperature Measurement 1. Introduction 2. Thermoelectric Effect Sensors (Thermocouples) 3. Varying Resistance Devices 4. Semiconductor Devices 5. Radiation Thermometers 6. Thermography (Thermal Imaging) 7. Thermal Expansion Methods 8. Quartz Thermometers 9. Fiber – Optic Temperature Sensors 10. Color Indicators 11. Change of State of Materials 12. Choice between Temperature Transducers sites.google.com/site/ncpdhbkhn 20