A quartz crystal sensor oscillator appropriate for highly viscous liquid measurements

摘要

This study describes a sensor oscillator appropriate for quartz crystal microbalance (QCM) based measurements in highly viscous liquids. The oscillator is stabilized by a recently developed impedance transformation QCM filter network which greatly reduces electrical load by the sustaining amplifier. In addition, it provides zero phase and a well-behaved symmetric resonance at the QCM series resonant frequency f_(s) over three orders of magnitude variation range of the motional resistance R_(m). The sustaining amplifier has constant pure resistive input and output impedances to eliminate phase shifts due to QCM impedance changes with liquid load. Also, it allows precise gain and phase control for accurate adjustment of the oscillator frequency at f_(s) and extraction of R_(m) information at the measured liquid load. The oscillator was tested with different water-based glycerol solutions in the 40-100 wt(percent) range. The worst-case frequency error was 4.7percent in this viscosity range.