0The measurement of viscosity is a large and complicated subject. The principles rely on the resistance to flow or the resistance to motion through a fluid. Many of these are covered in British Standards 188. The following is a brief description of some types.
The fluid is drawn up into a reservoir and allowed to run through a capillary tube to another reservoir in the other limb of the U tube. The time taken for the level to fall between the marks is converted into cSt by multiplying the time by the viscometer constant. ν = ct The constant c should be accurately obtained by calibrating the viscometer against a master viscometer from a standards laboratory.
