- Stokes law forms basic of this viscometer.
- Sphere of known diameter descend through liquid and time required to travel between two fiducial marks is measured.
- Errors might be due to friction against wall.
- The system is modified in terms of rolling ball where ball roll downs slope.
Falling Ball Viscometer uses the simple — but precise — Höppler principle to measure the viscosity of Newtonian liquids by measuring the time required for a ball to fall under gravity through a sample-filled tube.
The principle of the viscometer is to determine the falling time of a ball of known diameter and density through a close to vertical glass tube of known diameter and length, filled with the fluid to be tested. The viscosity of the sample liquid is related to the time it takes for the ball to pass a distance between two specified lines on the cylindrical tube.
Turning the measurement tube results in returning of the ball and it is possible to re-measure the time over the same distance. The result is dynamic viscosity with the standard dimension.