Brookfield RVDV-II+Pro - Page 71

Brookeld Engineering Labs., Inc. Page 71 Manual No. M/03-165-D0410
Example: Calculate the acceptable range of viscosity using RVDV-II+Pro with RV-3 Spindle
at 2 RPM; Brookeld 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 D2
SMC = 10 from Table D1
Full Scale Viscosity Range
1
*
10
*
10,000
=
50,000 cP
2
The viscosity is accurate to (+/-) 500 cP (which is 1% of 50,000)
2) The viscosity standard uid 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 Viscometer
is operating correctly. Any reading outside these limits may indicate a Viscometer problem.
Contact the Brookeld technical sales department or your local Brookeld dealer/distributor
with test results to determine the nature of the problem.
Example: Calculate the acceptable accuracy for viscosity measurement using LVDV-II+ Pro
with SC4-21 spindle in Small Sample Adapter at 6, 12, and 30 RPM. Brookeld
viscosity standard uid 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 Coefcient in
Appendix B of More Solutions to Sticky Problems or by using the Auto Range button on
your viscometer.
The Spindle Range Coefcient 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