Electromagnetically driven torsional resonators for viscosity and mass density sensing applications

• A cylindrical, torsional oscillator is used for measurements in liquids.
• Two prototypes differing in their actuation and read out mechanisms are compared.
• A complete analytical model relating the liquid's viscosity and mass density to measured resonance frequencies and quality factors is derived.
• The results of recorded frequency responses in ten different liquids are presented.

In this contribution a conceptual study for torsional oscillators, which are electromagnetically driven and read out, is presented. The aim is to experimentally investigate the basic feasibility of a torsional resonator with application to viscosity and mass density sensing in liquids. Such a device is particularly interesting as cylindrical, torsional resonators for fluid sensing applications are hardly reported but unlike many other devices, yield pure shear wave excitation in the liquid. The design of first conceptual demonstrators for measurements in air as well as in liquids and their benefits and disadvantages is discussed in detail. A closed form as well as a reduced order model and measurement results obtained with first demonstrators are presented.