Measurement unit for determining harmful gases esp. in air mixt. in passenger compartment of vehicle - preheats gas mixt. to be monitored to stipulated temp. to reduce effect of interference so that more sensitive gas sensor can be used

摘要

The power of the heating element (22) is regulated using an electrical regulating unit, having at least one regulator and an adjusting element. The measurement temp. is determined by a thermometer probe in the chamber (20). The measurement temp. can be determined using a thermometer probe in the heating element (22). The latter) is made of a material with a marked PTC characteristic, pref. a PTC ceramic. The gas sensor (10) is a semiconductor gas sensor constructed in layers. ADVANTAGE - Gives sensor signal with good stability. Regulation behaviour is stabilised in regulated operation of heating. Reduces temp. gradient between sensor and ambient air.