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Where:
TK = 1.0 from Table D-2
SMC = 10 from Table D-1
Full Scale Viscosity Range
2) The viscosity standard fluid is 12,257 cP. Its accuracy is (+/-)1% of 12,257 or (+/-)122.57 cP.
Total allowable error is (122.57 + 500) cP = (+/-) 622.57 cP.
3) Therefore, any viscosity reading between 11,634.4 and 12,879.6 cP indicates that the Viscometer is operating
correctly. Any reading outside these limits may indicate a Viscometer problem. Contact the AMETEK Brookfield
technical sales department or your local AMETEK Brookfield dealer/distributor with test results to determine the
nature of the problem.
Example:
Calculate the acceptable accuracy for viscosity measurement using DVPlus LV with SC4-21 spindle in
Small Sample Adapter at 6, 12, and 30 RPM. AMETEK Brookfield viscosity standard fluid 100 cPs has
an actual value of 101.5 cP at 25ºC.
1) Calculate the full scale viscosity range either by using the Spindle Range Coefficient in Appendix A of
Solutions to Sticky
The Spindle Range Coefficient for the 21 spindle on an LV Torque instrument is 4,688.
At 6 RPM, the Full Scale Range (FSR) viscosity is 781 cP. Allow +/- 1% for the Viscometer and +/- 1% for
the Small Sample Adapter. Total allowable accuracy is:
+/- 2% x 781 cP = +/- 15.6 cP
A similar calculation at 12 RPM gives FSR = 391 cP: +/- 2% x 391 cP = +/- 7.8 cP
A similar calculation at 30 RPM gives FSR = 156 cP: +/- 2% x 156 cP = +/- 3.1 cP
2) The Viscosity Standard Fluid is 101.5 cP. Its accuracy is:
+/- 1% x 101.5 cP = +/- 1.015 cP or roughly +/- 1.0 cP for further calculations.
3) Total accuracy is the sum of the values n (1) and (2):
At 6 RPM, accuracy is: 15.6 cP + 1.0 cP = +/- 16.6 cP
At 12 RPM, accuracy is: 7.8 cP + 1.0 cP = +/- 9.8 cP
At 30 RPM, accuracy is: 3.1 cP = 1.0 cP = +/- 4.1 cP
4) Therefore, at each speed, the acceptable windows within which the measured viscosity value must lie is calculated
relative to the viscosity value of the standard:
At 6 RPM: 84.9 cP to 118.1 cP
At 12 RPM: 91.7 cP to 111.3 cP
At 30 RPM: 97.4 cP to 105.6 cP
If your measured values fall outside of these windows, contact AMETEK Brookfield or your local
authorized dealer to discuss your results and determine whether your instrument is out of calibration.
M21-400 REV.1.1
Problems" or range shown on the configure viscosity test screen.
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
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