Brookfield DV3T Rheometer - Manual (Page 111)

Brookfield Engineering Labs., Inc. Page 111 Manual No. M13-2100
Brookfield Viscosity Standards Fluids are accurate to (+/-) 1% of their stated value.
Example: Calculate the acceptable range of viscosity using DV3TRV 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 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.
Example: Calculate the acceptable accuracy for viscosity measurement using DV3TLV
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
rheometer.
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 rheometer
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.