The system design of a Love wave sensor for measuring liquid dielectric constant

Compared with other acoustic sensors, the Love wave liquid sensor has obvious advantages. The precise measurement of the liquid dielectric constant is of great importance. When the liquid is non-viscous, only the liquid dielectric constant affects the Love wave propagation velocity and resonant frequency. In this paper, by the methods of the partial wave theory and the surface effective permittivity, according to the sensitivity and the electromechanical coupling coefficient, the delay-line type Love wave device made up of 36°YX LiTaO₃ substrate and SU-8 photoresist film is optimized and made. The phase difference measurement circuit and the amplitude-frequency characteristic measurement circuit are established with AD9912 as signal source module and AD8302 as signal acquisition module. Using different ratios of pure water and alcohol as the liquid samples, the experimental results are in accordance with the numerical simulations.