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 al lows the resonance frequency shift and the resonance damping to be stu died separately. Periodic oscillations of both signals between 1 and 1 0 ppm were observed. The wavelengths of the compressional waves, calcu lated from the periodicity of the signals, were in good agreement with theoretical values. (C) 1998 Elsevier Science B.V.