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Radiation Pyrometers
By: Niraj Trivedi120200117124
PyrometersPyrometry is a technique for measuring
temperature without physical contact. It dependsupon the relationship between the temperature ofhot body and eletronicmagnetic radiation emittedby the body.
It is a technique for determining a body’stemperature by measuring its eletronicmagneticradiation .
‘ Pyro’ is the ‘Greek’ word which means fire.
Two types of pyrometers used in industries :Radiation PyrometersOptical Pyrometers
A pyrometer has an optical system and detector. The optical system focuses the thermal radiation onto the detector. The output signal of the detector(Temperature T) is related to the thermal radiation or irradiance j* of the target object through the Stefan–Boltzmann law, the constant of proportionality, called the Stefan-Boltzmann constant and the emissivity ε of the object.
Black Body Spectrum
The radiation pyrometer has an optical system, including alens, a mirror and an adjustable eye piece. The heat energyemitted from the hot body is passed on to the optical lens,which collects it and is focused on to the detector with thehelp of the mirror and eye piece arrangement. The detectormay either be a thermister or photomultiplier tubes. Thoughthe latter is known for faster detection of fast movingobjects, the former may be used for small scale applications.Thus, the heat energy is converted to its correspondingelectrical signal by the detector and is sent to the outputtemperature display device.
ABILITY TO MEASURE HIGH TEMPNO NEED FOR CONTACTFAST RESPONSE SPEED
HIGH O/PMODERATE COST
Emissivity errors are introduced Errors due to the absorption of radiation by carbon dioxide,
water or other apparently transparent gases.
They are used for temperatures above the practical operating range of thermocouples. They can be used in the environments which contaminate or limit the life of thermocouple.Used for moving targets. They are used for measurement of average temperature of large surface areas. They are used for the targets which would be damaged by contact with primary elements like thermocouples and resistance thermometers.
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