A resonant sensor for liquid density measurement based on a piezoelectric bimorph

Density is one of the characteristic properties of a substance and on-line density sensors are of interest in many industrial fields. In this paper, a piezoelectric density sensor is proposed and analyzed with FE methods and experimentally. The active element of the proposed density sensor is a cheap piezoceramic bimorph, widely used in buzzers and telephone receivers; the bimorph is clamped all around tightening its border to the edge of a rigid open chamber in which the liquid is poured. The resonance flexural frequency of the membrane is modified by the liquid mass, the liquid volume is the volume of the chamber and therefore the liquid mass density can be obtained by the membrane resonance frequency variation. First measurements on an ad hoc realized prototype confirm the device capability.