Liquid Property Identification by Electro-Mechanical Impedance Method Using a 1-3 Piezoelectric Composite Sensor

Electro-mechanical impedance (EMI) method utilizing smart materials is an effective way for liquid property identification. In this article, we report on a 1-3 piezoelectric composite sensor used for identifying liquid property based on EMI method. To understand the operation mechanism of the sensor immersed in liquid, a fluid-structure interaction model was established. An analytical solution to govern the electrical impedance of the 1-3 piezoelectric composite sensor coupled with a liquid was derived. Based on the model, the influence of the acoustic impedance of a liquid on electrical impedance of piezoelectric materials is clearly revealed. The experimental results show that the measured acoustic impedance of 3 liquids using the fluid-structure interaction model agrees well with the reference values. The maximum relative error in the experiments is merely 2.4%, much less than that obtained by equivalent circuit model, confirming the accuracy of the model we built. Moreover, the 1-3 piezoelectric composite sensor based on EMI method exhibits a higher resolution than frequency drift method. The method presented provides a simple, cost-effective, and convenient way in liquid property identification.