Brookfield DV-III Ultra Rheometer - Manual (Page 50)

Brookfield Engineering Laboratories, Inc. Page 50 Manual No. M/98-211-B0104
Brookfield Engineering Laboratories, Inc. Page 50 Manual No. M98-211-E0912
This technique is fast and easy. It's well suited to gathering data on samples prior to establishing
a test method or for performing single point tests.
S DV-III SPEED/TIME PAIRS
DV-III speed/time pairs offers a simple technique to collect multiple data points. Programs can
be created and executed from the DV-III Ultra keypad. Results can be analyzed or output to a
printer.
This technique is useful when multiple data points are required and the test method is simple.
S B.E.V.I.S. PROGRAMS
B.E.V.I.S. Programs offer a command set capable of sophisticated rheometer control and data
collection. Programs are created on a PC and executed from the DV-III Ultra keypad. Results can
be analyzed or output to a printer.
The B.E.V.I.S. Program technique is useful when sophisticated data collection is necessary.
IV.5 Data Analysis for Viscosity Tests
Data collected from DV-III speed/time pairs or B.E.V.I.S. programs may be analyzed using several
math models. These models provide a means to numerically describe the behavior of the test fluid.
In the case of viscosity measurement, a non-Newtonian fluid will produce a curve when test data
is plotted on a shear stress vs. shear rate graph. The math model will force the data into a straight
line and describe it with a slope and y intercept. The terminology associated with the slope and y
intercept vary from model to model as does the interpretation of results. (See Appendix for more
information on math models.)
The DV-III Ultra does not allow for data sets to be edited. Programs must be constructed to conform
with the following data requirements if math models are to be used:
• The data set must contain non zero values for shear stress and shear rate (except for the
paste model which requires non zero viscosity and RPM).
• There cannot be two equal adjacent shear rate values (RPM values for paste model).
• % torque values of all data points must be between 0.1% and 100%.
If any of the above circumstances are violated, an error message will appear when a math
model is selected.
ERROR #1: A % torque value is less than 0.1. A shear stress or shear rate value is
zero.
ERROR #2: A % torque value is greater than 100.
ERROR #3: Reserved
ERROR #4: Two adjacent speeds of equal value.
Math models for data analysis are accessed by pressing the PROG key and then 3; 3 = Models
(Figure IV-1). If no data (i.e. no data at all or less than two (2) data points) is in the data buffer, no
modeling can be performed and Figure IV-39 will be displayed: