Miniaturized viscosity and mass density sensors combined in a measuring cell for handheld applications

Miniaturized viscosity sensors are attractive devices for condition monitoring applications involving fluid media. Previously introduced devices utilize vibrating resonant mechanical structures interacting with the fluid where the resonance frequency and the quality factor are affected by the fluid's viscosity and mass density. The investigation of many of these devices showed instabilities in their resonance frequencies and high cross-sensitivities e.g., to temperature. To overcome these drawbacks, we designed new resonant sensor principles based on U-shaped electrical conductors interacting with the sample liquid, which are presented and discussed in this contribution. For measuring the viscosity with resonant principles, it is necessary to know the liquid's mass density. Hence, we integrated a separate mass density sensor in our measuring cell. We present first measurement data obtained with these devices and discuss their sensitivity to viscosity and mass density.