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Sensor Physics Non contact temperature measurement Dr. Seres István.

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Presentation on theme: "Sensor Physics Non contact temperature measurement Dr. Seres István."— Presentation transcript:

1 Sensor Physics Non contact temperature measurement Dr. Seres István

2 SENSOR PHYSICS Dr. Seres István 2 Thermometers based on thermal radiation Electromagnetic spectra c = f namevawelengthFrequency AC> 3000 km< 100 Hz Radiovawes< 30 km> 10 kHz Longvawe range (LW)< 10 km> 30 kHz medium vawe range (MW)< 650 m> 650 kHz short vawe range (KW)< 180 m> 1,7 MHz Ultrashort range(URH)< 10 m> 30 MHz Microvawes300 µm - 30 cm1 GHz - 1 THz Infrared radiation (IR)< 1,0 mm> 300 GHz Visible light< 780 nm> 384 THz red nm THz orange nm THz yellow nm THz green nm THz blue nm THz violet nm THz Ultraviolet radiation (UV)< 380 nm> 789 THz Röntgen radiation< 1 nm> 300 PHz Gamma-radiation< 10 pm> 30 EHz

3 SENSOR PHYSICS Dr. Seres István 3 Thermometers based on thermal radiation Theory: black body Definition: it absorbs all the EM radiation Its model: hole in a wall

4 SENSOR PHYSICS Dr. Seres István 4 Thermometers based on thermal radiation Theory: Planck law for radiation The power emitted by the unit surface of a T temperature object :

5 SENSOR PHYSICS Dr. Seres István 5 Thermometers based on thermal radiation /the difference is < 1%, if T < 3000  m∙K/ If, than the law can be written as: Theory: Planck law for radiation

6 SENSOR PHYSICS Dr. Seres István 6 Thermometers based on thermal radiation Where (for what ) is the maximum value of the function? /the derivetive there is zero/ Theory: Planck law for radiation

7 SENSOR PHYSICS Dr. Seres István 7 Thermometers based on thermal radiation Theory: Wien law Where (for what ) is the maximum value of the function? /the derivetive there is zero/

8 SENSOR PHYSICS Dr. Seres István 8 Thermometers based on thermal radiation the color of the warming iron is changing the blue stars are hotter Theory: Wien law

9 SENSOR PHYSICS Dr. Seres István 9 Thermometers based on thermal radiation Theory: Stefan-Boltzmann law How much is the integral of the function ( 0< <∞)? – /partial integration/  = 5,67∙10 -8 W/m 2 K 4 St

10 SENSOR PHYSICS Dr. Seres István 10 Thermometers based on thermal radiation  = 5,67∙10 -6 W/m 2 K T k the temperature of the environment, K – depends on the surfaces and distances Theory: Stefan-Boltzmann law

11 SENSOR PHYSICS Dr. Seres István 11 Thermometers based on thermal radiation Theory: gray body Kirchhoff law Independent from the material properties

12 SENSOR PHYSICS Dr. Seres István 12 Thermometers based on thermal radiation Theory: gray body

13 SENSOR PHYSICS Dr. Seres István 13 Thermometers based on thermal radiation Infra thermometer The effect of the air, the transmission coefficient of the air at different vawelengths

14 SENSOR PHYSICS Dr. Seres István 14 Thermometers based on thermal radiation Infra thermometer Effektív vawelength The calibration function of an infra thermometer: Where N is:

15 SENSOR PHYSICS Dr. Seres István 15 Thermometers based on thermal radiation Infra thermometer Main parts: detector termopile (seriel connection of thermocouples, photo-detektor –photovoltaic pyro-electric optical system


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