These sensors are designed for gas detectors and analysers. Their principle of operation consists in absorption of infrared radiation by some gases (hydrocarbons, carbon monoxide and dioxide).
Only narrow range of infrared spectrum, characteristic for a given gas is absorbed. The knowledge of this phenomenon make possible to design sensors fitted with filters for wavelength responding to relevant gases. Comparing the value measured by such a sensor with the value measured by the reference filter (G20 for wavelength 4ľm) makes possible detection and measurement of given gas concentration in the air.