Owner manual

Brookfield Engineering Laboratories, Inc. Page 37 Manual No. M/98-211-A0701
IV.5 Data Analysis
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.
The DV-III+ 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
20). 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 57 will be displayed:
Figure 57
If there is already data in the data buffer, the user will be presented with the following screen:
Figure 58