Brookfield Engineering Laboratories, Inc.
Page 119
Manual No. M98-211-E0912
5) Connect the sample cup to the Rheometer. Allow sufficient time for temperature to reach
equilibrium. Typically 15 minutes is the maximum time that you must wait. Less time is required
if spindle and cup are already at test temperature.
6) Measure the viscosity and record the Rheometer reading in both % torque and centipoise
(cP).
Notes:
1) The spindle must rotate at least five (5) times before a viscosity reading is taken.
2) The use of Brookfield Viscosity Standard fluids in the range of 5 cP to 5000 cP is recommended
for cone/plate instruments. Please contact Brookfield Engineering Laboratories or an authorized
dealer if your calibration procedure requires more viscous standards.
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. Do not use a
silicone viscosity standard fluid with a viscosity value greater than 5000 cP with a Cone/Plate
Viscometer. Brookfield offers a complete range of mineral oil viscosity standards suitable
for use with Cone/Plate Viscometers as shown in Table E-2. Consult with Brookfield or an
authorized dealer to determine which fluid is appropriate.
Interpretation of Calibration Test Results
:
When verifying the calibration of the DV-III Ultra, the instrument and viscosity standard fluid error
must be combined to calculate the total allowable error.
The DV-III Ultra is accurate to (
+
/-) 1% of any full scale spindle/speed viscosity range.
Brookfield Viscosity Standards Fluids are accurate to (
+
/-) 1% of their stated value.
Example 1
: Calculate the acceptable range of viscosity using RVDV-III with RV-3 Spindle at 2
RPM; Brookfield Standard Fluid 12,500 with a viscosity of 12,257 cP at 25
°
C:
1) Calculate full scale viscosity range using the equation:
Full Scale Viscosity Range [cP] = TK * SMC * 10,000
RPM
Where:
TK = 1.0 from Table D-2
SMC = 10 from Table D-1
Full Scale Viscosity Range = 50,000 cP
1 * 10 * 10,000
2
The viscosity is accurate to (+/-) 500 cP (which is 1% of 50,000)
2) The viscosity standard fluid is 12,257 cP. Its accuracy is (
+
/-)1% of 12,257 or (
+
/-)122.57 cP.
3) Total allowable error is (122.57
+
500) cP = (
+
/-) 622.57 cP.
4) Therefore, any viscosity reading between 11,634.4 and 12,879.6 cP indicates that the Rheometer
is operating correctly. Any reading outside these limits may indicate a Rheometer problem.
Contact the Brookfield technical sales department or your local Brookfield dealer/distributor
with test results to determine the nature of the problem.
