M19-2101 REVISION 2.0 DVNEXT RHEOMETER - OPERATIONAL MANUAL
Solutions to Sticky Problems" or by using the Auto Range button on your rheometer.
The Spindle Range Coecient 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.
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.
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