Brookfield Engineering Laboratories, Inc. Page 29 Manual No. M/92-021-N0902
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 spindle and chamber geometry will
affect the viscosity readings. If one reading is taken at 2.5 rpm, and a second at 50 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 of the spindle, the size
and shape of the spindle, the size and shape of the container used and therefore, the distance between
the container wall and the spindle surface.
A repeatable viscosity test should control or specify the following:
1) Test temperature
2) Sample container size (or spindle/chamber geometry)
3) Sample volume
4) Viscometer model
5) Spindle used (if using LVDV-I+ (#1-4) or RVDV-I+ (#1-7) attach the guard leg)
6) Test speed or speeds (or the shear rate)
7) Length of time or number of spindle revolutions to record viscosity.
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