n.
Instrument for measuring the viscosity (resistance to internal flow) of a fluid .
In one type, the time taken for a given volume of fluid to flow through an opening is recorded. In the capillary-tube viscometer, the pressure needed to force the fluid to flow at a specified rate through a narrow tube is measured. Other types depend on measurements of the time taken for a sphere to fall through the fluid, or of the force needed to rotate the inner cylinder of a pair (the space between the two cylinders being filled with the fluid under test), or of the rate at which oscillations of a disk vibrating in the fluid die out.