Low maintenance high pressure viscometer

Viscometer with a rotor rotatable by a coupling magnet and a driving magnet to shear a tested fluid thus imparting torque to a bob mounted on a bob shaft supported via a pair of bob shaft bearings. A spiral spring restricts the rotation of bob shaft. Magnetometer measures the angular position of a top magnet connected to the top of bob shaft. This angular position information is further converted to the viscosity of the tested fluid.