Mineral oil temperature-dependent viscosity and viscosity index are determined from damping of excited magnetostrictive rod at differing temperatures to assure e.g. marine engine oil is fit for purpose

摘要

A magnetostrictive sensor rod (13) immersed in the liquid, is pulsed into longitudinal oscillation, the viscosity being inferred from damping of the oscillations. Temperature is controlled to a low value. The liquid, in a closed container, is stirred, promoting flow along the rod. The viscosity is then measured. Lastly, stirring is re-commenced and the temperature is raised to a new, higher level. The new viscosity is measured. Viscosity measurement follows an interval of calm, without stirring. An Independent claim is included for the corresponding viscometer. Key features include excitation of the rod by a coil (11) fed with electrical pulses, a temperature sensor (12) and the cylindrical vessel (2) employed for heating and mixing. Preferred features: The viscosity index is determined from two viscosity values taken at upper and lower reference temperatures. Measurements are taken repeatedly to calculate the average. Flow along the rod (13) is promoted by the spiral stirrer (16) parallel to it.