Is an oscillator-based measurement adequate in a liquid environment?
Oscillator-based measurements with quartz crystal resonators will be analyzed. The investigations have shown that classical thickness monitors as well as many chemical vapor sensors based on a quartz crystal microbalance (QCM) work properly, even with simple oscillators. It was demonstrated that, for applications in a liquid environment, more sophisticated electronics are necessary. Also a comparison between the experimental results in liquids and the theoretical predictions is hardly possible without the knowledge of the oscillator behavior. As our solution, we present an automatic gain-controlled oscillator with two output signals, the oscillator frequency, and a signal that represents the damping of the quartz resonator. A calibration method is introduced, which allows one to calculate the series resonance frequency fs and the series resistance Rs from these oscillator signals.
Borngräber
Ralf
R
Institute for Micro- and Sensor Systems, Otto-von-Guericke-University, Magdeburg, Germany. Ralf.Lucklum@E-Technik.Uni-Magd
Schröder
Jens
J
Lucklum
Ralf
R
Hauptmann
Peter
P