Gas thermal conductivity sensor based on SAW

An uncoated surface acoustic wave (SAW) delay line integrated with a suitable film heater is used as a gas sensitive element based on thermal conductivity change. It detects concentrations from 0.1-100% of H/sub 2/, O/sub 2/, He, and Ar in N/sub 2/ in the temperature range from 20-150/spl deg/C. The value and sign of the SAW gas response are controlled by substrate material and reference gas.