Modeling approaches for electrodynamically driven viscosity and mass density sensors operated in the kHz range and experimental verifications

Modeling approaches for resonant viscosity and mass density sensors operated in the kHz range are presented. As a common feature, recently investigated devices (oscillating membranes, platelets and beams) are electrodynamically driven and read out. By sweeping the excitation current, the frequency response containing a characteristic resonance can be recorded. Depending on the particular sensor design, the shape of the frequency responses might be influenced by spurious additional signals associated with the sensor´s ohmic resistances, parasitic and mutual inductances, capacities, the effect of the liquid´s conductivity and permittivity. Furthermore, the ambient temperature often also plays a significant role on these aforementioned additional signals. In this paper, we present a unified framework suitable for modeling these kinds of sensors for the case of an oscillating U-shaped wire sensor and demonstrate the validity of the devised models by comparison with experimental results. The focus of the presented modeling is on the explanation of the additional spurious signals occurring in the frequency response.