SELECTIVE GAS-DETECTION USING UNCOATED SAW DELAY-LINES

Two approaches for gas recognition in binary mixtures have been develo ped for uncoated surface acoustic wave (SAW) sensors based on gas ther mal conductivity principle. The first approach utilizes the difference thermal conductivity of the ambient atmosphere with respect to a refe rence gas as general property to test the responses of the sensing ele ments. Selecting the operating temperature and the reference gas, a si ngle gas is distinctly detected. The second approach is based on the i nherent property of the SAW devices, whose response is monitored by th e temperature coefficient of delay (TCD). Choosing the operating tempe rature and the substrate material, the SAW response for a test gas is rejected. Experimental measurements are shown and discussed. (C) 1997 Elsevier Science S.A.