Network analysis based interface electronics for quartz crystal microbalance

The application of resonant sensors such as quartz crystal microbalance (QCM) resonators requires interface electronics to measure parameters that characterize sufficiently the resonant behavior of the sensor due to effects under investigation. Common oscillators as sensor electronics have two major disadvantages. Since they measure the resonant frequency shift as the only parameter their employment is restricted to mass sensing of thin and rigid films in terms of QCM. Because of spurious phase shifts the measured resonant frequency may be erratic. In order to characterize the sensor itself or a material on the sensor surface more parameters such as damping are to be measured. Therefore, a sensor electronics was developed that precisely acquires the impedance spectrum of the resonant sensor in a small frequency range which reflects properties like thickness of a sensor coating, its density, and shear moduli or the density-viscosity product when measuring in liquids. Originally developed as a sensor interface electronics this novel device can help researchers to investigate any effects or material parameters affecting the impedance spectrum of the sensor. In this article the measurement concept of the network analysis based device will be explained followed by details of realization on single printed cardboard. Measurement errors are estimated by simulation and by a comparison of measurement results from a commercially available network analyzer as a reference. Examples of laboratory and industrial applications will be given. (C) 2001 American Institute of Physics.