Principle:
It is based on the principle of absorption of total radiation from hot body.
Construction and Working:
It consists of blackened tube open at one end to receive the radiation from the hot body
whose temperature is to be measure.
The other end of the tube has a sighting aperture in which an adjustable eyepiece is
fitted.
The thermal radiation from hot body strike on the concave mirror.
Position of the mirror can be adjusted by rack and pinion arrangement for focusing the thermal radiations on the detector disk.
The detector disk is a platinum sheet
The disk is connected to the thermocouple
The leads from the detector disc are used for measuring thermoelectric EMF.
Advantages
Non-contact
Accurate
Versatile
Inexpensive
Disadvantages
Can be affected by ambient conditions
Can be difficult to use
Can be damaged by high temperatures
Applications
Industrial processes
Scientific research
Medical diagnostics
