Brookfield RVDV-II+Pro - Special Considerations; Effect on accuracy when using accessory devices

Brookeld Engineering Labs., Inc. Page 59 Manual No. M/03-165-D0410
Special Considerations
In taking viscosity measurements with the DV-II+Pro Viscometer there are two considerations
which pertain to the low viscosity limit of effective measurement.
1) Viscosity measurements should be accepted within the equivalent % Torque Range
from 10% to 100% for any combination of spindle/speed rotation.
2) Viscosity measurements should be taken under laminar ow conditions, not under
turbulent ow conditions.
The rst consideration has to do with the precision of the instrument. All DV-II+Pro
Viscometers have an accuracy of +/- 1% of the range in use for any standard spindle or cone/
plate spindle. (Note that accuracy values may be higher than 1% when using accessory devices
with the DV-II+Pro). We discourage taking readings below 10% of range because the potential
viscosity error of +/- 1% is a relatively high number compared to the instrument reading.
The second consideration involves the mechanics of uid ow. All rheological measurements
of uid ow properties should be made under laminar ow conditions. Laminar ow is ow
wherein all particle movement is in layers directed by the shearing force. For rotational
systems, this means all uid movement must be circumferential. When the inertial forces on
the uid become too great, the uid can break into turbulent ow wherein the movement of
uid particles becomes random and the ow can not be analyzed with standard math models.
This turbulence creates a falsely high Viscometer reading with the degree of non-linear
increase in reading being directly related to the degree of turbulence in the uid.
For the following geometries, we have found that an approximate transition point to turbulent
ow occurs:
1) No. 1 LV Spindle: 15 cP at 60 RPM
2) No. 1 RV Spindle: 100 cP at 50 RPM
3) UL Adapter: 0.85 cP at 60 RPM
Turbulent conditions will exist in these situations whenever the RPM/cP ratio exceeds the values
listed above.
Eect on accuracy when using accessory devices
The Brookeld viscometer has a stated accuracy of +/- 1% of the range in use. This stated
accuracy applies when the viscometer is used in accordance with the operating instructions
detailed in the instrument instruction manual and the calibration test uid is used in accordance
with the instructions provided by the uid supplier (including the critical parameters of
temperature control and stated uid accuracy). Brookeld’s accuracy statement of +/- 1% of
the range in use applies to the Brookeld rotational viscometer when used with the standard
spindles supplied with the instrument, including LV spindles 1 through 4 (supplied with LV
series viscometers), RV spindles 2 through 7 (supplied with RV series viscometers), and HV
series spindles 2 through 7 (supplied with HA series viscometers and HB series viscometers) in
a 600 ML low form Grifn beaker.
Brookeld offers a range of accessories for use with the Brookeld viscometer to
accommodate special measurement circumstances. These accessories, while offering added
capability to the user, also contribute to an expanded measurement tolerance beyond the
instrument accuracy of +/- 1% of the range in use. This expanded measurement tolerance is
a function of many parameters including spindle geometry, accessory alignment accuracy,
sample volume requirement, and sample introduction techniques. The effect of these