Measurements of Liquid Density and Viscosity with Flexural Resonators Using Noise as an Excitation Source

As it was shown in other publications, the flexural resonators placed in fluid environment demonstrate changes in their impedance compared to the impedance in vacuum. It was also shown that those changes could be measured and used to calculate the fluid density and viscosity. If the resonator is made of piezoelectric material or driven by piezoelectric actuator, the equivalent electrical impedance of the resonator can be measured directly and related to its mechanical impedance through the electromechanical coupling coefficient. Quartz tuning forks are among the most common resonators of this kind. Naturally occurring noise can be used as an excitation source for the impedance measurements within frequency range that allows deciphering the properties of the fluid in which the resonator is immersed.