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D. Janneau:
"Viscosity measurement techniques using Thickness-Shear Mode";
Betreuer/in(nen): B. Jakoby; Institut für Sensor- und Aktuatorsysteme, 2003.

A Thickness-Shear Mode resonator (TSM) is an acoustic wave sensor whose working principle is based on piezoelectricity. Its main component is a quartz substrate. This piezoelectric material has the ability to become electrically polarized when it undergoes mechanical stress or strain by applying an AC-voltage. Thus, the sensor can be excited to perform shear oscillations. Furthermore, a liquid which loads the electrode surface of such a sensor can be viscously entrained by the mechanical oscillation induced by the electrical excitation of the sensor. Hence, the viscosity of the fluid can be measured, because this liquid loading modifies the electrical properties of the sensor, namely its admittance. In order to build a complete viscosity measurement system, different means can be used. On the one hand, the TSM can be connected to a network analyzer. This network analyzer is connected to a computer, and the s21 sensor s-parameter is retrieved with LabVIEW. With the help of Matlab, we get an estimate for the sensor equivalent circuit elements. As an alternative, an electronic oscillator with a differential amplifier as a main component and the quartz as frequency-determining element, was built to convert the fluid´s viscosity into a frequency. Finally, an application concerning the monitoring of the crystallization of a protein, the lysozyme, was considered using the network analyzer approach.