Brookfield DV-II+ Digital Viscometer - Manual (Page 37)

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4) The viscosity standard fluid, together with the spindle, should be immersed in the bath for a
minimum of 1 hour, stirring the fluid periodically (operate at 50 or 60 RPM periodically), prior
to taking measurements.
5) After 1 hour, check the temperature of the viscosity standard fluid with an accurate thermometer.
6) If the fluid is at test temperature ( + /- 0.1
°
C of the specified temperature, normally 25
°
C),
measure the viscosity and record the viscometer reading.
Note: The spindle must rotate at least five (5) times for one minute, whichever is greater
before readings are taken.
7) The viscosity reading should equal the cP value on the viscosity fluid standard to within the
combined accuracies of the viscometer and the standard (as discussed in the section entitled,
Interpretation of Calibration Test Results).
Calibration Procedure for Cone/Plate Viscometers:
1) Follow the procedures outlined in Appendix A for mechanically adjusting the setting of the cone
to the plate.
2) Refer to Appendix A, Table 1, and determine the correct sample volume required for the spindle
to be utilized.
3) Select a viscosity standard fluid that will give viscosity readings between 10% and 100% of full
scale range. Refer to Appendix B for viscosity ranges of cone spindles. Consult with Brookfield
or an authorized dealer to determine which fluid is appropriate.
It is best to use a viscosity standard fluid that will be close to the maximum viscosity for a given
cone spindle/speed combination.
Example: LVDV-II + Viscometer, Cone CP-42, Fluid 10
Having a viscosity of 9.7 cP at 25
°
C
At 60 RPM, the full scale viscosity range is 10.0 cP. Thus, the Viscometer reading should be
97% torque and 9.7 cP viscosity
±
0.197 (closer to
±
0.2) cP. The accuracy is a combination of
Viscometer and fluid tolerance (refer to Interpretation of Calibration Test Results).
4) With the viscometer stopped, remove the sample cup and place the viscosity standard fluid into
the cup, waiting 10 minutes for temperature equilibrium.
5) Connect the sample cup to the Viscometer. Allow 10 minutes for temperature to reach
equilibrium.
6) Measure the viscosity and record the Viscometer reading in both % torque and centipoise (cP).
Note: The spindle must rotate at least five (5) times before a viscosity reading is taken.
Interpretation of Calibration Test Results:
When verifying the calibration of the DV-II+, the instrument and viscosity standard fluid error must be
combined to calculate the total allowable error.
The DV-II+ is accurate to (+/-) 1% of any full scale spindle/speed viscosity range.