Surface-Acoustic-Wave, Array Analyzer for Measuuremnent of Carbon-Dioxide, Oxygen, and Ethylene

Surface Acoustic Wave (SAW) devices have shown some promise as specific gas detector/analyzers for a number of applications. These sensors operate as dual oscillators in which one SAW is coated with a sorbent material specific to c particular gas. The frequency of the coated oscillator changes with gas concentration while the uncoated reference oscillator does not. The difference between the frequency of the two oscillators is an indicator of gas concentration. Most previously developed SAW gas sensors have been limited to the measurement of a single specific gas species. Because it is difficult to isolate a sorbent material that is specific to a single gas species, interferences from other gas species will usually degrade instrument performance. This research project will investigate a different approach to SAW gas concentration measurement in which an array of four SAW delay line oscillators each coated with a different sorbent material will be used to create a series of frequency shift patterns for each gas species. These vapor patterns will be inputs to a pattern recognition software program in a microcomputer that will determine the chemical concentration of c whole range of gas species. The extensive background and experience of Biotronics in complex pattern recognition offer a high probability of success for this project. A number of sorbent coatings have been identified for O2 and CO2 that will provide a robust set of frequent shift pattern parameters.