A new type humidity sensor using micro-air-bridge heaters

A new type absolute-humidity sensor with very quick response, very small power consumption and high sensitivity, which is based on the detection of the thermal conductivity change in humid air at heated temperature above 400°C, has been developed and demonstrated. Since this new type absolute-humidity sensor is able to be easily heated up above 400°C within 30–40 msec because of a micro-air-bridge heater structure, the surface of its sensing area is refreshed by burning out adsorbed dusts, oil, etc. Thermal conductivity _mix of mixed gas expressed by Sutherland-Wassiljewa equation is applied to the humid air to study this absolute humidity sensor. Only a single micro-air-bridge heater operation driven by double pulse-currents for this humidity sensor is also proposed.