Brookfield CAP2000 Viscometer User Manual
Page 27
Brookfield Engineering Labs., Inc.
Page 27
Manual No. M/94-310F
Viscometer Related Variables
Most fluid viscosities are found to be non-Newtonian. They are dependent on Shear Rate and the
spindle geometry conditions. The specifications of the Viscometer cone and plate geometry will affect
the viscosity readings. If one reading is taken at 400 rpm, and a second at 1,000 rpm, the two viscosity
values produced will be different because the readings were made at different shear rates. The faster
the spindle speed, the higher the shear rate.
The shear rate of a given measurement is determined by the rotational speed and the cone angle.
A repeatable viscosity test should control or specify the following:
1.
Viscometer model
2.
Cone used
3.
Test temperature
4.
Test speed(s) [or the shear rate(s)]
5.
Length of time to record viscosity
6.
Sample volume sufficient to cover the face of the cone