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R. Schnitzer, C. Reiter, K.-C. Harms, E. Benes, M. Gröschl:
"A computer-controlled remote measurement system for resonant BAW sensors";
in: "Proc. IEEE Sensors 2004", D. Rocha, P.M. Sarro, M. Vellekoop (Hrg.); IEEE, 2004, S. 798 - 801.

A novel microprocessor-controlled remote measurement
system for resonant piezoelectric bulk acoustic wave (BAW)
sensors is presented. The system supports various sensor
types for different physical quantities such as temperature,
humidity, viscosity, density and speed of sound of liquids,
and film thickness. The measurement principle is based on
the determination of locus of admittance curves of the respective
sensors for one or several resonances (fundamental
and/or overtones). Measurement results are calculated
from the measured resonance frequencies or quality factors
by applying the appropriate sensor function for each type
of sensor. The system covers sensors with resonance frequencies
ranging from 30 kHz to 30 MHz. Special electronics
have been developed to transform the sensor admittance
values to voltage signals that are acquired by the
computer system. Disturbing effects caused by the capacitance
of the sensor connecting cable are minimized by
special electronic circuitry.
Keywords
piezoelectric sensor, quartz crystal, viscosity sensor, sensor
interface electronics, remote measurement

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