Sensor based on piezo buzzers for simultaneous measurement of fluid viscosity and density

Abstract

A novel low cost sensor is proposed to measure simultaneously viscosity and density of Newtonian fluids. In the proposed configuration, the sensor is built with two piezoelectric buzzers disks. One disk is excited with a step signal while the other is used to read the sensor response. Damping factor and resonant frequencies are measured when the sensor is immersed in fluids of different densities and viscosities. Excitation signal and data acquisitions are phase locked, therefore ensemble averaging techniques are employed to improve signal to noise ratio. Binary mixtures of glycerol and ethanol are selected for assessment of sensor capabilities. Due to the high temperature dependency of fluid viscosities a parametric variation of the fluid properties could be achieved by varying the fluid temperature. Dynamic response of the sensor is calibrated against the fluid properties for viscosities up to 200 cP and densities up to 1.23 g/cm3. Estimated uncertainties are ±8 cP and ±0.03gm/cm3, with 95% of confidence, for viscosity and specific gravity, respectively. These uncertainties include sensor sensitivity to temperature. Results are promising and show a proof of concept. Thus, disposable and very low cost devices can be developed based on the proposed sensor.