Brookfield DV2T Viscometer - Manual (Page 67)

Brookfield Engineering Labs., Inc. Page 67 Manual No. M13-167-B0614
Viscometer Related Variables
Most fluid viscosities are found to be non-Newtonian. They are dependent on Shear Rate, time
of test 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 cP 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
6) Whether or not to attach the guard leg
7) Test speed or speeds (or the shear rate)
8) Length of time or number of spindle revolutions to record viscosity
9) How the sample was prepared and/or loaded into the container