A high frequency shear wave impedance spectrometer for low viscosity liquids

A method for measuring the complex shear viscosity spectra of low viscosity liquids in the frequency range 6-120 MHz is described. Details of the resonator cell, based on a thickness shear (AT-cut) quartz resonator as central device, and of the RF bridge circuit for the compensation of the unloaded capacitance of the resonator are presented. A measuring and data-evaluation procedure that allows the careful consideration of spurious higher order vibration modes and also of intrinsic cell losses is discussed. Sources of experimental error are shown and the usability of the method is illustrated by reference measurements. The complex viscosity spectrum of n-dodecanol is displayed and its relaxation frequency is compared with the value resulting from broad-band acoustical attenuation spectrometry.