Brookfield RVDV-II+Pro - A.5 Viscosities of Distilled Water and a 5 CPS Standard @ 25°C Tested with Cone Spindles #40 and #41

Brookeld Engineering Labs., Inc. Page 54 Manual No. M/03-165-D0410
A.5 VISCOSITIES OF DISTILLED WATER AND A 5 CPS STANDARD @ 25°C TESTED WITH
CONE SPINDLES #40 AND #41.
Distilled water and a 5 CPS Brookeld Viscosity Standard Fluid rated 4.7 cP and at 25°C
were tested using a Brookeld LVDV-II+Pro C/P Viscometer with Cone Spindles CPE-40 and
CPE-41. Temperature was maintained at 25°C by using a Brookeld TC-502P Programmable
Temperature Bath. Samples were equilibrated at 25°C for 15 minutes prior to testing.
Conditions were used such that results were between 10 and 100% of Full-Scale Range or
“FSR”.
The attached graph shows that the viscosity of each material, when measured with the CPE-
40 Cone Spindle, is essentially constant over the range of speeds tested. However, viscosity
increases with increasing speed for each material when using Cone Spindle CPE-41. This
agrees with viscosity behavior discussed in the technical literature on the same subject. That
is, the chance of secondary ows and therefore, erroneous readings, increases as:
1. the sample viscosity decreases,
2. the cone angle increases, and
3. the cone angular velocity (or testing speed) increases.
Figure A7 summarizes the results for viscosity vs. speed. Note that the 0.90 cP reading, for
distilled water was made at 40 rpm (11.5% Torque) corresponding to 300 s
-1
. Liquids with
higher viscosities may be measured with on-scale torques at lower speeds (and shear rates).
Therefore, if it is desired to test very-low-viscosity materials at very-low-shear rates, the tester
should seriously consider using an air-bearing instrument with a low-angle cone.
Figure A-7: Distilled water and 5 CPS standard results at 25°C.