Modeling of piezoelectric tube resonators for liquid sensing applications

A model for the electrical impedance of a fluidic piezoelectric tube sensor, resonating in thickness-wall-mode, is presented. The tube is mechanically loaded with acoustic impedances which represent the fluid properties. It is shown that the electrical impedance of a plane resonator model yields results very close to the tube model, if the static capacitance of the tube is used with the plane impedance expression. Therefore, the common transmission line models may furthermore be used with minor changes. Measurement results are compared with the cylindrical model and with the plane approximation.