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The first consideration has to do with the precision of the instrument. All DVNext Rheometers 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 DVNext). 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 fluid flow. All rheological measure me of fluid flow properties
should be made under laminar flow conditions. Laminar flow is flow wherein all particle movement is in layers
directed by the shearing force. For rotational systems, this means all fluid movement must be circumferential. When
the inertial forces on the fluid become too great, the fluid can break into turbulent flow wherein the movement of
fluid particles becomes random and the flow can not be analyzed with standard math models. This turbulence
creates a falsely high rheometer reading with the degree of non-linear increase in reading being directly related to
the degree of turbulence in the fluid.
For the following geometries, we have found that an approximate transition point to turbulent flow occurs:
•
No. 1 LV Spindle:
•
No. 2 LV Spindle:
•
No. 1 RV Spindle:
•
No. 2 RV Spindle:
•
UL Adapter:
•
SC4-18/13R:
The AMETEK Brookfield rheometer has a stated accuracy of +/- 1% of the range in use. This stated accuracy
applies when the rheometer is used in accordance with the operating instructions detailed in the instrument
instruction manual and the calibration test fluid is used in accordance with the instructions provided by the fluid
supplier (including the critical parameters of temperature control and stated fluid accuracy). AMETEK Brookfield's
accuracy statement of +/- 1% of the range in use applies to the AMETEK Brookfield rotational rheometer when used
with the standard spindles supplied with the instrument, including LV spindles 1 through 4 (supplied with LV series
rheometers), RV spindles 2 through 7 (supplied with RV series rheometers), and HV series spindles 2 through 7
(supplied with HA series rheometers and HB series rheometers) in a 600 mL low form Griffin beaker.
AMETEK Brookfield offers a range of accessories for use with the AMETEK Brookfield rheometer 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 elements
on measurement tolerance must be considered when verifying the calibration of your AMETEK Brookfield rheometer.
Sample temperature in all test circumstances is very important and will also add an additional expanded tolerance
depending on the temperature control system and the calibration verification tests begin with the standard
rheometer spindles as detailed above.
Once the calibration of the rheometer itself is confirmed, the expanded tolerance of the measurement system may
be determined using accessory devices. In many cases, this additional tolerance will be very minimal, but as a general
statement, the addition of +/- 1% of the range in use is reasonable for accessories.
M19-2101 REVISION 2.0
15 cP at 60 RPM
100 cP at 200 RPM
100 cP at 50 RPM
500 cP at 60 RPM
0.85 cP at 60 RPM
1.25 cP at 240 RPM
D V N E X T R H E O M E T E R - O P E R AT I O N A L M A N U A L
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