Contactless identification of liquid types in thin-walled container using electromechanical impedance of a 1-3 piezoelectric composite sensor

The electromechanical impedance (EMI) method has been applied to liquid identification due to its sensitivity and adaptability in challenging environments. In this paper, we propose a contactless identification of liquid types in thin-walled containers using a 1-3 piezoelectric composite sensor. A fluid-structure coupling model that accounts for the influence of container wall thickness on sensor impedance is developed. An analytical expression for the impedance of a 1-3 piezoelectric transducer, accounting for coupling with a container wall and liquid, has been derived. To validate the proposed model, two methods, directly measuring the sensor impedance and measuring voltage variations across a resistor, and three different liquids are employed. Compared with theoretical liquid impedance, the maximum experimental error is only 2.7 %. Results confirmed reliability and accuracy of the model we proposed. The method presented provides a precise, adaptable solution for contactless identification of liquid types in thin-walled containers using a 1-3 piezoelectric composite sensor.