LIQUID VISCOSITY MEASUREMENT USING SH WAVE-PROPAGATION CHARACTERISTICS ON PIEZOELECTRIC CERAMIC THIN PLATE

Liquid viscosity measurement using shear horizontal (SH) wave propagation characteristics on a piezoelectric ceramic thin plate is described. The mode conversion loss associated with the compressional component U3 is zero, because the SH wave on the piezoelectric ceramic substrate poled along the horizontal axis has only the horizontal component U2, The IDT has a much larger electromechanical coupling factor for the S0 mode SH wave than that of the SH surface acoustic wave (SAW). The metal-coated condition of the liquid-loaded surface is essential for detecting the liquid viscosity. There exists a linear relationship between the fractional phase velocity change of the S0 mode and the square root of the liquid viscosity. The measured results on liquid viscosity using the S0 mode SH wave devices, for some concentrations of glycerol-water solutions, are in good agreement with the theoretical prediction.