C1.2 - A Compact Subsampling Impedance Analyzer for Resonating Sensors

Abstract

Resonant sensors are used in a wide range of applications, e.g. as microbalances, chemical sensors in liquid and gaseous environments, and for physical property sensing of liquid and viscoelastic media [1]. Our sensor electronics [2] will be used for the readout of resonant sensors for liquid properties, which means that the Q–factor of such devices is much lower than that of resonators operating in vacuum or gaseous environments. Hence oscillator circuits are not preferable evaluation circuits for this application. Moreover, the damping may be frequency dependent, so measurement over a wide frequency range is mandatory. Besides the common method of using precise laboratory instruments for the measurement of the impedance spectra of these sensors, various approaches have been reported [3–8]. For the interpretation of the measurement results not only the amplitude but also the phase angle of the sensor impedance is of interest allowing a more accurate characterization of the resonance behavior. In this paper we introduce the system concept and some measurement results in comparison to results obtained with a commercial lock–in amplifier.