Viscometers

A viscometer for testing the viscosity of a fluid, comprising a rotor that engages with a stator, the rotor being coupled to a drive means capable of rotating the rotor with respect to the stator, there been a separation gap between the stator and the rotor for the accommodation of fluid to be tested, and measurement means for measuring the characteristics of the rotor and/or stator such that the viscosity of the fluid can be determined. The drive means accelerates the rotor from rest or from a low rotational speed which does not significantly affect the specified test temperature of the rotor, stator and test fluid, to the required angular velocity, and the measurement of the required characteristics are taken, all within a time period sufficiently short such that no temperature change significant to the calculation of the viscosity occurs. The required angular velocity is such that rotating the rotor at or near this velocity for longer than the said time period would cause a temperature change significant to the calculation of the viscosity to occur.