Kirchoff's law- Optical Pyrometer

Asked by  | 14th Apr, 2008, 12:37: PM

Expert Answer:

It just means that the body will acquire the temperature of the enclosure.
Optical Pyrometers work on the 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. The optical system contains filters that restrict the wavelength-sensitivity of the devices to a narrow wavelength band around 0.65 to 0.66 micons (the red region of the visible spectrum).


Other filters reduce the intensity so that one instrument can have a relatively wide temperature range capability. Needless to say, by restricting the wavelength response of the device to the red region of the visible, it can only be used to measure objects that are hot enough to be incandescent, or glowing. This limits the lower end of the temperature measurement range of these devices to about 700 °C.Some experimental devices have been built using light amplifiers to extend the range downwards, but the devices become quite cumbersome, fragile and expensive.

Answered by  | 15th Apr, 2008, 07:50: PM

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