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Sensor Physics Non contact temperature measurement Dr. Seres István

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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

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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

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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 :

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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

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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

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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/

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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

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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

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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

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

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

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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

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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:

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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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