Brookfield DV2+Pro Viscometer Manual do Utilizador descarregar pdf (Página 72)

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Brookeld Engineering Labs., Inc. Page 72 Manual No. M03-165-F0612

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.2LVSpindle: 100cPat200RPM

3) No.1RVSpindle: 100cPat50RPM

4) 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

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