Integrated array of SAW sensors for gas analysis

A new approach, based on the properties of SAW devices, is used to integrate an array of gas sensors into a single substrate, using a single chemical membrane. The different response of each individual device to the same set of gases is provided by different acoustic propagation conditions, only. Three four-sensor prototypes have been implemented on ST-cut quartz substrates, using different Pd films as membrane. Their response upon exposure to concentrations of H/sub 2/, N/sub 2/O and CO in N/sub 2/ and to water humidity have been tested. A strong dependence of the response versus the acoustic propagation direction has been demonstrated for all the prototypes analyzed.