Simultaneously measurement of frequency shift and series resistance changes of a quartz resonator using a miller QCM oscillator

In this work it is shown that a Miller quartz crystal microbalance (QCM) electronic oscillator circuit can be used to simultaneously measurement of the resonant frequency shifts and changes in the motional resistance of the resonator. In order to calibrate the sensitivity to variations in the series resistance of the resonator, an experiment was carried out with the resonator immersed in liquids at different concentrations of glycerol. Also the sensor system has been applied to control the series resistance during the water uptake in a cataphoretic organic coating. It was observed that the series resistance remains constant during the experiment in the absence of changes in the damping of the resonator (there are no viscoelastic changes in the coating). Moreover, we have studied amplitude fluctuations of the sensor system, determining the sensor resolution in the resistance measurements.