Brookfield DV-I Prime - Manual (Page 40)

Brookfield Engineering Laboratories, Inc. Page 40 Manual No. M/07-022-D0613
When comparing data with others, be sure to specify the sample container and
presence/absence of the guardleg.
Many samples must be controlled to a specific temperature for viscosity measurement.
When conditioning a sample for temperature, be sure to temperature control the container
and spindle as well as the sample.
Please see our publication, “More Solutions to Sticky Problems”, for more details relating
to sample preparation.
III.3 Selecting a Spindle/Speed
The DV-I PRIME has the capability of measuring viscosity over a wide range (for example, the
RVDV-I PRIME can measure fluids within the range of 100-13,000,000 cP) (see Appendix B).
This range is achieved through the use of several spindles over many speeds.
The process of selecting a spindle and speed for an unknown fluid is normally trial and error. An
appropriate selection will result in measurements made between 10-100 on the instrument
% torque scale.
Two general rules will help in the trial and error process.
1. Viscosity range is inversely proportional to the size of the spindle.
2. Viscosity range is inversely proportional to the rotational speed.
In other words: to measure high viscosity, choose a small spindle and/or a slow speed. If the
chosen spindle/speed results in a reading above 100%, then reduce the speed or choose a smaller
spindle.
Experimentation may reveal that several spindle/speed combinations will produce satisfactory
results between 10-100%. When this circumstance occurs, any of the spindles may be selected.
Non-Newtonian fluid behavior can result in the measured viscosity changing if the spindle and/
or speed is changed. See our publication, “More Solutions to Sticky Problems,” for more detail.
When viscosity data must be compared, be sure to use the same test methodology: the same
instrument, spindle, speed, container, temperature and test time.
III.4 Multiple Data Points
The majority of viscosity measurements are made at the quality control level and often consist
of a single data point. The test is conducted with one spindle at one speed. The data point is a
useful benchmark for the go/no-go decision in a production setting. The DV-I PRIME can be
used for single point measurement.
Many fluids exhibit a characteristic change in viscosity and yield stress with a change in applied
force. This non-Newtonian flow behavior is commonly seen in paints, coatings and food products
as a decrease in viscosity as shear rate increases or an increase in yield stress as rotational speed