Viscosity sensor with temperature measurement function based on multifunctional metal matrix composite

Abstract

A temperature-compensated viscosity sensor was developed. The sensor consisted of a multifunctional metal matrix composite incorporating a metal-core piezoelectric fiber and a surface-oxidized metal fiber. This viscosity sensor was developed as a sensor that can withstand harsh environments, such as engine oil monitoring. In this case, viscosity is affected by oil deterioration, sludge mixing, and temperature changes. Therefore, a multifunctional metal matrix composite was fabricated using two metal-core piezoelectric fibers for viscosity measurements, and a surface-oxidized metal fiber for temperature. The metal oxide surface has a notch made by removing the oxide film, which forms a thermocouple when it comes into contact with the metal matrix. After evaluating the device's characteristics in standard room temperature, the viscosity was measured using glycerine solutions with different concentrations and varying temperatures. The temperature dependence of the sensor was measured and used for calibrating the results. This temperature dependence was present due to changes in dimensions due to thermal expansion of the matrix, and Young's modulus, piezoelectric constant, and relative dielectric constant of the piezoelectric ceramic fibers. A correction formula was calculated based on temperature dependence to demonstrate that temperature compensation was possible at range of from 2 to 25 Pa s kgm3.