Brookfield DV-III Rheometer - Manual (Page 60)

Brookfield Engineering Laboratories, Inc. Page 60 Manual No. M/98-211-A0701
full scale range precision of (+/-) 1% of any spindle/speed combination. We discourage taking readings
below 10% of range because the potential viscosity error of (+/-) 1% is a relatively high number
compared to the instrument reading.
The second consideration involves the mechanics of fluid flow. All rheological measurements of fluid
flow properties should be made under laminar flow conditions. Laminar flow is flow wherein all particle
movement is in layers directed by the shearing force. For rotational systems, this means all fluid
movement must be circumferential. When the inertial forces on the fluid become too great, the fluid can
break into turbulent flow wherein the movement of fluid particles becomes random, and the flow can not
be analyzed with standard math models. This turbulence creates a falsely high Rheometer reading, with
the degree of non-linear increase in reading being directly related to the degree of turbulence in the fluid.
For the following geometries, we have found that an approximate transition point to turbulent flow
occurs:
1) No. 1 LV Spindle: 15 cP at 60 RPM
2) No. 1 RV Spindle: 100 cP at 50 RPM
3) UL Adapter: 0.85 cP at around 70 RPM
4) SC4-18/13R: 1.25 cP at around 240 RPM
Turbulent conditions will exist in these situations whenever the RPM/cP ratio exceeds the values listed
above.