Viscosity tester and method with orbiting object

摘要

A viscosity tester includes a free standing magnetic object disposed in fluid in a stationary receptacle. A magnetic force drives the object in an orbit and the magnetic force, the speed of the object and the lag angle between the magnetic field and the object are either measured or controlled and, based on at least one of these three parameters, the viscosity of the fluid is determined. In one embodiment, a magnetic ball is driven by four electromagnets, with proximity sensors detecting the presence of the ball and controlling the electromagnets. In another embodiment, a free standing magnet is driven in an orbital pattern by a rotating field that is coaxial with the orbital pattern and is produced by a rotating magnet or a stator.