Design of a high precision falling-ball viscometer

Abstract

The increase in uncertainty throughout the viscosity scale being the principal disadvantage of capillary viscometry, an absolute falling-ball viscometer has been developed, making it possible to cover a wide range of viscosities while keeping a weak uncertainty. The measurement of viscosity of a liquid then rests on the terminal velocity measurement of a falling ball, corrected by the principal identified effects (edge effects, inertial effects, etc.). An experimental bench was developed in order to reach a relative uncertainty of the order of 10−3 to the measure of viscosity. The bench, by the use of a linear camera, allows us to observe the trajectory and to obtain the variations in velocity of the ball inside a cylindrical tube filled with liquid whose viscosity is to be measured.