A Surface Acoustic Wave Gas Detector

Abstract

Abstract : Experimental results are presented on a new type of gas detector employing surface acoustic waves (SAW's). The SAW piezoelectric gas detector (SAWPG) consists of twin SAW delay lines fabricated on a single piezoelectric substrate each connected in an oscillator configuration. The propagation path of one delay line oscillator is coated with a selectively sorbent film, while the other is uncoated and used as a stable reference. Changes in phase delay resulting from mass loading or stress effects induced by gases sorbed on the delay line containing the film result in corresponding frequency shifts relative to the reference oscillator that are proportional to gas concentration. Since SAW energy is concentrated near the film, the detector is found to be highly sensitive. Further, the SAWPC offers the means to detect any gas given the corresponding selectively sorbent film.