Feasibility of Using Piezoelectric Probes to Measure Viscosity in Newtonian Fluids

Viscosity plays an important role in modeling fluid flow in different systems. In Newtonian fluids, viscosity is a constant, measureable property. Currently, viscosity is measured using viscometers that use an array of different techniques depending on the application. In this study, pre-stressed lead zirconate titanate (PZT) composites were used as probes to monitor changes in viscosity. The probes are used as an actuator-sensor pair: a voltage of 1Vrms will be applied to one probe, the actuator; the second probe, the sensor, receives a vibration wave and turns it into an output voltage. Measurements of gain and phase at different input signal frequencies are analyzed. The fluid-medium where the probes are tested consists of different glycerin-deionized water solutions. Results indicate that the frequency of peak phase shift can be correlated to fluid viscosity. This correlation is exponential with viscosity, with an R2 of 0.99. Results included viscosity values in the range of 0.8cP to 612cP. Possible applications for this type of sensor are numerous, and are both non-time-dependent (simple viscosity measurements of fluids), and time-dependent.