Methanol sensor using a shear horizontal surface acoustic wave (SH-SAW) device

Measurements of liquid properties are important for industry, environmental issues, and human life. Because a surface acoustic wave on 36YX-LiTaO3 is a shear horizontal (SH) mode, the liquid-phase SAW sensor is realized using a crystal. In this paper, we present a SH-SAW-based methanol sensor that functions at high temperature. The SH-SAW propagation characteristics were calculated using a numerical calculation method considering temperature coefficients of the substrate and liquid. Calculation results indicate that the SH-SAW sensor can detect methanol solutions at temperature greater than 50 °C. Moreover, the calculated results suggest that the sensor sensitivity increases with increasing temperature. The methanol solutions were measured using the SH-SAW sensor. Concentration and temperature of the methanol solution were varied. Linear relationships between sensor responses and concentration were observed at each temperature. As the numerical calculation results suggest, the sensor sensitivity increases with increased temperature. Based on the experimental results, the detection limit of the sensor was estimated as 0.10% by weight at 60 °C.