What is the working principle of Radiation pyrometer? What are the advantages and disadvantages?

Pyrometers are used to measure the temperature which is difficult to measure. They are non-contact devices, used to measure temperature above 1500 degree Celsius, contact devices may melt at this temperature.


The pyrometer has an optical system, including a lens, mirrors and adjustable eyepiece and a detector circuit.

An optical system collects the visible and infrared energy from an object and focuses it on a detector.


The heat energy emitted from the hot body is allowed passed on to the lens. Which collects it and focused on to the detector with the mirror and eyepiece arrangement.

Now the detector converts the radiation energy into an electrical signal. Thermophiles and photon multipliers are commonly used detectors. Detectors produce the reading and shows in the temperature display.


  • Low cost

  • N need of contact

Fast response speed


  • Emissitive error are introduced

  • Error due to the obsortion of the radiation by the carbon dioxide , water or other apparently transparent gases