Process for determining gas concentrations comprises simultaneously modulating the temperature of the sensitive layer and the electrical field to control the sensitivity

摘要

Process for determining gas concentrations comprises applying a heating voltage to a heating element (5) to heat a sensitive layer (1) of the gas sensor; producing an electrical field in the sensitive layer and measuring the electrical resistance of the sensitive layer. The temperature of the sensitive layer and the electrical field are simultaneously modulated to control the sensitivity of the sensitive layer for individual gas concentrations of a gas mixture. An Independent claim is included for a thin layer semiconductor gas sensor comprising a sensitive layer (1), a heating element (5) and a control device (7). Preferred Features: The heating voltage is periodically changed to produce variations of the electrical field in the sensitive layer. The modulation of the temperature and the electrical field is carried out with a frequency of at least 0.1, preferably 0.26 Hz. By adjusting the modulation frequency, the sensitivity of the sensitive layer for reducing gases, especially CO, is reduced whilst it remains constant for oxidizing gases, especially NO2 and/or O3.