Application of a Piezoelectric Resonator for Reconstructing the Parameters of a Contacting Liquid

The effect of conductive and nonconductive liquids on the characteristics of a piezoelectric longitudinal-electric-field resonator immersed in a liquid was studied. The resonator, operating on a longitudinal acoustic mode with a frequency of nearly 4 MHz, was an X-cut langasite disk with round electrodes on both sides. The resonator was fastened at the base of a container filled with the studied liquid. Then, the real and imaginary parts of its electrical impedance were measured as a function of frequency by a vector network analyzer. An upgraded electromechanical circuit taking into account the effect of the conductivity and dielectric permittivity of a liquid on the change in the effective surface area of electrodes was constructed for such a resonator. The possibility of determining the elastic modulus and viscosity coefficient of a studied liquid and the values of additional equivalent circuit elements by fitting the calculated frequency dependences of the complex electrical impedance of a resonator immersed in a liquid to the measured dependences was demonstrated.