A NEW APPROACH TO SELECTIVITY IN METHANE SENSING

A sensor selective to methane with respect to ethanol vapour has been constructed by using a multifunctional device which delivers three ele ctrical signals proceeding from two sensors, a main one and a referenc e one. The main sensor provides two signals: one reflecting the conduc tivity change of a Pd-doped tin dioxide thick film, and the other the temperature increase due to combustion processes, enhanced in the case of ethanol, but minimized for methane for which convection phenomena were shown to prevail. The latter signal is compared to a third one wh ich measures the temperature of a reference sensor, constructed in suc h a manner to be insensitive to gas combustion phenomena, but to react in a similar way as the main sensor to convection phenomena, i.e. cha nges in ambient conditions of temperature and of gas flow.