Detection of hazardous vapors including mixture in different conditions using surface acoustic wave device array

In this research, a surface acoustic wave (SAW) sensor was used for chemical compounds detection such as ammonia, methane, and ammonia/methane mixture gases. The detection results of ammonia/methane mixture gases by polymer deposited on 128° YX-LiNbO₃ SAW delay lines were presented. To enhance the sensitivity and accuracy of the surface acoustic wave sensors, the sensing chamber and polymer films was improved. Very low concentration of ammonia (~250 ppb) and methane(~9 ppm) could be detected by this SAW sensor. From the sensing database of ammonia and methane, we Figured out that the frequency shift of ammonia/methane mixtures was equal to the sum of frequency shift of ammonia and methane. Besides, the signal loss of ammonia was much stronger than methane in high relative humidity conditions. Here, superposition effect between ammonia and methane sensing signals could be used for the signal intensity prediction of different concentrations ammonia/methane mixture gases.