High frequency probe for the measurement of the complex viscosity of liquids

A high frequency rheological measurement device based on resonant torsional oscillations of a titanium tube is proposed. The measurement is entirely based on a digital phase measurement and a single electromagnetic device plays the roles of both actuator and sensor, successively. It is shown that the measured probe behaviour is in good agreement with theoretical predictions for fluids which can be considered as Newtonian at the probe working frequency of about 5.6 kHz. Viscoelastic fluids are also measured, and the obtained complex viscosity appears to corroborate lower frequency measurements. The simplicity of the device, its good resolution in the 0.3–500 mPa s viscosity range and the calibration-free approach as well as the particular tubelike geometry make it an interesting instrument for the high frequency rheological characterization of fluids in both laboratory and industrial environments.