Improvement of humidity dependence in gas sensor based on SnO2

A tin oxide-based gas sensor for detecting CH4 and i-C4H10 in a low gas concentration (200 ppm) was developed on the basis of “Hot Wire Type” gas sensor, which was sintered in a bead (0.55 mm ∅) to cover a platinum wire (0.20 mm ∅) coil. The effect of oxides of Co, Cr, La or Ce on humidity dependence of tin oxide was investigated. The oxides of Co and Cr gave a prominent stability for the sensor output to CH4 and i-C4H10 under the humidity change outdoors through a year.