A method is described for background gas (BG) analysis in surface acoustic wave (SAW) gas sensors using two frequencies. The gas parameter G is defined as the square root of molecular weight times the ratio of specific heat at constant pressure to specific heat at constant volume, which is a representative property of BGs. In an experiment using varying BGs, the measured G values agreed with the true values. The concentrations of mixed BGs were successfully measured. This method will be useful in a trace moisture analyzer in natural gases and in the optimization of the purge process of glove boxes.
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