SAW gas detection using uncommon delay lines

SAW delay lines with three different geometries are experimentally investigated as gas detectors and suggested for sensing of corrosive analytes. The main feature of these geometries is the complete separation between electromechanical transducers and sorbent film deposited on the opposite sides of substrate Experiments are accomplished at room temperature and atmospheric pressure with delay lines implemented on glass, quartz and Bi/sub 12/SiO/sub 20/ substrates and operating at frequencies 28-263 MHz. Pt film and H/sub 2/ exposure are exploited as an example to demonstrate applicability of the proposed geometries as gas detectors. Comparison between the uncommon and common delay lines as gas sensors shows approximately the same gas sensitivity (50 ppm at 0.1% Hz), but higher insertion loss for uncommon devices. Achievable limits of the losses are discussed. Gas responses for SAW delay lines with different geometries, materials and wrap-around transits are presented.