METHOD AND A SIMPLE APPARATUS FOR RAPID SIMULTANEOUS MEASUREMENT OF RESONANCE FREQUENCY AND Q-FACTOR OF A QUARTZ-CRYSTAL

The quartz crystal microbalance is finding many novel uses beyond its traditional utility as a thin film deposition controller. In many situ ations where the quartz crystal is immersed in a viscous fluid, it is desirable to measure the crystal's Q factor in addition to its resonan ce frequency. Here, we describe a simple method for simultaneous measu rement of the resonance frequency, the quality factor, and the activit y or relative amplitude of oscillation of a quartz crystal in vacuum a nd in gaseous environment. The hardware, comprising of a synthesized s ine wave generator and a phase detector, passively interrogates the cr ystal to determine its resonance frequency and activity. The passive m easurement system can detect a resonance even when the crystal is heav ily damped. Representative measurement results for an AT-cut quartz cr ystal in a number of gases at various pressures are presented. The met hodology described here may be readily applied to quartz crystals imme rsed in a liquid. (C) 1996 American Institute of Physics.