Signal oscillations of a piezoelectric quartz crystal in liquids caused by compressional waves

Fluctuations in the signal of a piezoelectric quartz crystal in water and methanol are described as resonance effects of compressional waves. The evaporation of the fluid layer, which acts as a resonant cavity, is modelled on the laws of diffusion. Measurements were performed on 10 MHz AT-cut quartz crystals by the network analysis method, which allows the resonance frequency shift and the resonance damping to be studied separately. Periodic oscillations of both signals between 1 and 10 ppm were observed. The wavelengths of the compressional waves, calculated from the periodicity of the signals, were in good agreement with theoretical values.