Brookfield DV2T Viscometer - Manual (Page 78)

Brookfield Engineering Labs., Inc. Page 78 Manual No. M13-167-B0614
Small Sample Adapter, UL Adapter, Thermosel, Spiral Adapter, and DIN Adapter, the
accuracy value may be increased. In general the increase in accuracy will be minimal,
however, it could be as much as 1% for a total accuracy of +/- 2% of the range in use.
Brookfield Viscosity Standards Fluids are accurate to (+/-) 1% of their stated value.
Example:
Calculate the acceptable range of viscosity using DV2TRV 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 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 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 Viscometer is operating correctly. Any reading outside these limits may indicate a
Viscometer problem. Contact the Brookfield technical sales department or your local
Brookfield dealer/distributor with test results to determine the nature of the problem.
Example:
Calculate the acceptable accuracy for viscosity measurement using
DV2TLV with SC4-21 spindle in Small Sample Adapter at 6, 12, and 30
RPM. 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 B of More Solutions to Sticky Problems or by using the Auto Range button
on your viscometer.
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