Basics of Infrared Thermometry      99- 
 
Figure 48: 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.