Total Radiation Pyrometer – Diagram , Working , Advantages

Total Radiation Pyrometer – Diagram , Working , Advantages

Thermal radiation is an electromagnetic radiation emitted by a body as a result of its temperature. Thermal radiation is in the wavelength region from about 0.1-100 µm.

The total radiation emitted by a blackbody is given by , Eb = σ x T ^4


  • σ  is the Stefan Boltzmann constant (5.669 x 10^-8 W/m^2 y,
  • Eb is the emissive power, and
  • T is the absolute temperature in K.

Construction :

The total radiation of pyrometer has one housing tube in which an adjustable eye piece is fixed at one end of the housing tube and the other end is free to receive radiations from the radiating object whose temperature is to be measured. A rack and pinion attachment is used to adjust the position of a concave mirror (Figure ). A thermocouple is also provided to receive the radiation and the thermocouple is
connected to the milli voltmeter to measure the temperature.

total radiation pyrometer diagram
total radiation pyrometer diagram


Thermal radiations from the radiating object come inside the housing tube. These radiations fall on the concave mirror and they are reflected to the hot junction of the thermocouple. So, an e.m.f. will be produced in the thermocouple and it is measured by using a milli voltmeter. This change in e.m.f. will give the measure of temperature.


  • It is used to measure the high temperature of 3500°C.


  1. It has high accuracy
  2. There is no physical contact with the radiating object
  3. The distance between radiating object and pyrometer is negligible


1. It is not suitable for very low temperature measurement due to poor sensitivity.
2. Dust, smoke, gases in between radiating object and instrument will cause error.

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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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