直接冷凝式声表面波气体传感器检测下限分析

声表面波气体传感器有采用选择性敏感膜进行气体吸附和气体直接冷凝在声表面波器件表面(与气相色谱系统结合)进行检测两种方式.文中首先从分层介质理论出发,分别对涂敷敏感膜和直接冷凝这两种方式下声表面波器件表面质量负载改变引起的频率变化进行理论分析,比较了两种方式在吸附同样气体条件下的灵敏度;然后计算了在500 MHz工作频率、考虑冷凝液膜轻度粘滞性时,直接冷凝方式的气体检测下限为ppb量级;最后将计算结果与实验结果进行比较并得到验证.

Analysis on Threshold-detection-limit of Surface Acoustic Wave Gas Sensor with Direct-Condensation Mode

Two kinds of mode-sensitive-film mode and direct-condensation mode (combining SAW gas sensor with gas chromatography (GC))were used for surface acoustic wave gas sensor to detect undefined gas. Based on the theory of layered material structure, the frequency variety caused by the variety of the mass cohered on the surface of the piezoelectric substrate was analyzed on the condition of the two kinds of mode respectively. The sensitivities of SAW gas sensor with sensitive-film mode and SAW gas sensor with direct-condensation mode had been compared on the condition that the mass load were equal of two sensors. Then the threshold-detection-limit of the surface acoustic wave gas sensor with direct-condensation mode was calculated to be ppb level on the condition that the working frequency was 500 MHz and the liquid thin layer was considered low-grade viscosity. The theory simulation was validated by the experiment results finally.