optris PI 200 Operator's Manual page 75

Basics of Infrared Thermometry
Figure 45: Main principle of non-contact thermometry
Infrared thermometers basically consist of the following components:

Lens

Spectral filter

Detector

Electronics (amplifier/ linearization/ signal processing)
The specifications of the lens decisively determine the optical path of the infrared thermometer, which is
characterized by the ratio Distance to Spot size. The spectral filter selects the wavelength range, which is
relevant for the temperature measurement. The detector in cooperation with the processing electronics
transforms the emitted infrared radiation into electrical signals.
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