Measurement of methanol solutions using love mode liquid sensor

Controlling the methanol concentration is a key factor in improving the efficiency of the direct methanol fuel cell. In this study, the immersed-type Love mode sensor based on SiO₂/ST-cut Y-propagation quartz was fabricated for monitoring the methanol concentration. A temperature controlled measurement system consisting of a spectrum analyzer and an oscillator circuit was employed to characterize the methanol solutions with different weight concentrations at different temperatures. A theoretical prediction of the phase velocity shift for the methanol solutions with different weight concentrations was also performed for comparison. The results of methanol solutions with different weight concentrations at different temperatures show that the amount of the frequency shift is approximately linearly proportional to the weight concentration, and the proportional rate increases as the temperature increases. The concentration resolutions were 1.1876 and 0.2484 %/kHz by weight at 25°C and 70°C.