Operation principle of infrared thermometers

Infrared radiation is a part of sunlight which can be decomposed reflecting it through a prism. This radiation has energy. At the beginning of the 20th century, Scientifics Planck, Stefan, Boltzmann, Wien and Kirchhoff defined the electromagnetic spectrum activities and established comparations to describe infrared energy.
This makes possible to define energy in relation to wavelengths emitted by a black body. Objects with a temperature over absolute zero can irradiate energy. The amount of energy grows in proportion to the fourth magnitude of the temperature.
This concept is the Basic principle in the measurement of the temperature by means of infared. With the emission factor a variable is introduced. The emission factor is a measure for the relationship betweens radiations emitted by both a grey and a black body at the same temperature. A grey body is an object whose wavelengths have the same emission factor. The emission factor of a grey body does not change with the wavelength, as for instance Aluminium. In general, the emission factor is the same as the absorption factor..
For bright surfaces, the emission factor can be automatically or manually adjusted to correct measurement errors in infrared thermometers. When the emission factor is not constant two or more wavelengths should be measured to solve the problem.
Infrared thermometers are manufactured with many diverse applications. There are differences between them such as: their optical and electronic components, their technology, size or case. Infrared thermometers share a signal processing chain which starts with a IR signal and ends with a electronic output signal. This generic measurement chain begins with an optical system of lenses and / or conductors of light waves, filters and the detector.  

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