Brookfield DV3T Rheometer - Manual (Page 102)

Brookfield Engineering Labs., Inc. Page 102 Manual No. M13-2100
Rheometer 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 Rheometer 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) Rheometer 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