Numerical Analysis of Piezoelectric Sensor Using Multimode Vibration for Liquid Density and Viscosity Measurement

We report a new piezoelectric sensor for measuring the density and viscosity of liquids. This sensor can selectively vibrate in directions normal and tangent to the contact surface between the sensor and a liquid by choosing appropriate driving methods. In the proposed system, the density and viscosity can be presumed simply by measuring resonance frequencies in air and liquid for the vibration in the tangent and normal directions instead of measuring resonance frequency and damping of a single vibration mode for use in conventional method. In this report, we firstly derive a theoretical model of a plate vibrating in two directions with respect to the contact surface. Next, the proposed device is designed and evaluated by the finite element method (FEM). The validity of this calculation is ensured by comparison of an early experimental result and the result of the FEM. From this analysis, we find that the density and viscosity of a sample liquid were presumed within 2% error. (c) 2010 The Japan Society of Applied Physics