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The first consideration has to do with the precision of the instrument. All DVPlus Viscometers have an accuracy of
+/- 1% of the range in use for any standard spindle. (Note that accuracy values may be higher than 1% when using
accessory devices with the DVPlus). 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 measurements 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 Viscometer 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:
1.
No. 1 LV Spindle:
2. No. 2 LV Spindle:
3. No. 1 RV Spindle:
4. No. 2 RV Spindle:
5. UL Adapter:
6. SC4-18/13R:
Turbulent conditions will exist in these situations whenever the RPM/cP ratio exceeds the values listed above.
Effect on accuracy when using accessory devices
The AMETEK Brookfield
applies when the
Viscometer
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
with the standard spindles supplied with the instrument, including LV spindles 1 through 4 (supplied with LV series
Viscometer), 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 Griffin beaker.
AMETEK Brookfield offers a range of accessories for use with the AMETEK Brookfield
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 Viscometer.
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
Viscometer
spindles as detailed above.
Once the calibration of the
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.
M21-400 REV.1.1
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
Viscometer
has a stated accuracy of +/- 1% of the range in use. This stated accuracy
is used in accordance with the operating instructions detailed in the instrument
Viscometer
itself is confirmed, the expanded tolerance of the measurement system may
D V P L U S D I G I TA L V I S C O M E T E R - O P E R AT I O N A L M A N U A L
Viscometer
when used
Viscometer
to accommodate
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