An Online Viscosity Measurement Method Based on the Electromechanical Impedance of a Piezoelectric Torsional Transducer

In this paper, we proposed an online viscosity measurement method based on the electromechanical impedance (EMI) of a piezoelectric torsional transducer. During testing, the contact torsional resonance of the cylindrical rod or host structure system is actuated and sensed by the ring array of shear mode piezoelectric patches. According to the quantitative electromechanical equivalent model we derived, the viscous damping from the contact fluid can be obtained by tracking the change of the piezoelectric impedance. A series of viscosity measurements was conducted on glycerol-water solutions of various concentrations, and the measurement results agree well with that given by standard laboratory viscometers. As the torsional vibration is a pure in-plane shear mode, which is more sensitive to the viscous damping and features a high quality factor, the proposed EMI-based measurement method is effective and promising for online viscosity measurement, especially for medium to high viscosity fluids.