Malvern Visco 88, Руководство пользователя, Страница: 38 / 74

Chapter 4 Other tasks
Page 4-4 MAN 0378
Calculating rheological data
Using the rotational speed V (rpm), the torque M (mNm) and the measuring sys-
tem constants, the shear stress, shear rate and viscosity can be calculated as follows:
„
Shear stress (Pa):
τ
= Cl * M
„
Shear rate (s
-1
): = C2 * V (where V = f(Hz) x 2 π)
„
Viscosity (Pas): η =
τ
/
The Cl and C2 measuring system values for constant set 1 are listed below:
Note
The rad
-1
units are displayed as rad/s in the software.
When parallel plates are used:
„
For constant sets 6 and 8 constants quote the shear stress at the perimeter.
„
For constant sets 3 , 5 and 7 constants quote the shear stress at the 3/4 radius.
Changing measuring system constants
The instrument is programmed to use a set of constants. This enables the instru-
ment to be run using any measuring system, for example a double gap system,
without the need for special software.
There should be no need to change from set 1 , the default, for cup and bob. For
cone and plate/parallel plate measuring systems, use set 5 .
Label Measuring system C1 (Pa/mNm) C2 (rad
-1
)
C14 DIN 1 15470 11.526
C25 DIN 2 27160 11.526
C30 DIN 3 15720 11.526
C14 infinite sea 4 15470 1.996
C25 infinite sea 5 27160 1.996
C30 infinite sea 6 15720 1.996
C14 wide gap 7 15470 2.435
C25 wide gap 8 27160 4.698
γ.
γ.
i