A theoretical model is established to describe the response mechanism of
surface acoustic wave (SAW) gas sensors based on physical adsorption on the detector
surface. Wohljent’s method is utilized to describe the relationship of sensor output
(frequency shift of SAW oscillator) and the mass loaded on the detector surface. The
Brunauer-Emmett-Teller (BET) formula and its improved form are introduced to depict the
adsorption behavior of gas on the detector surface. By combining the two methods, we
obtain a theoretical model for the response mechanism of SAW gas sensors. By using a
commercial SAW gas chromatography (GC) analyzer, an experiment is performed to
measure the frequency shifts caused by different concentration of dimethyl
methylphosphonate (DMMP). The parameters in the model are given by fitting the
experimental results and the theoretical curve agrees well with the experimental data