A viscosity sensor utilizing an electromagnetically actuated oscillating sphere

We present a novel viscosity sensor principle which uses an oscillating metal sphere attached to a wire acting as mechanical spring. The oscillation is electromagnetically excited using four actuation coils. The arrangement of the coils allows a linear oscillation in one plane but also a circular motion if the actuation coils are driven accordingly. The latter causes a constant speed of the sphere and thus a stationary flow around the sphere, which allows probing a different rheological regime (more comparable to conventional falling ball viscometers) compared to the oscillation mode featuring continuous acceleration and deceleration.