Table of Contents
Advertisement
Figure 3-34
Figure 3-35
Select Temperature Controller and you will be presented with the Default Temperature menu (see Figure 3-35). This
menu allows the user to 1) initiate communication with the temperature controller and 2) set a default temperature.
Initiate temperature control by pressing the Test Connection. The connection status will be confirmed with a message
box and the appearance of the bath icon in the status bar (see Section 2.3).
The Default Temperature is the temperature value that the control device will return to at the conclusion of a Test.
This value is set only if the check box is checked. When the check box is unchecked, the temperature controller will
hold at the last set point used in the Test.
TIP: When a test involves several temperature set points, set the Default Temperature to the first set point used in
the Test. This will reduce the transition time from one Test run to the next Test run.
Note that temperature controllers can also be controlled through the RheocalcT software when they are connected
to the computer using the proper cable. The Thermosel requires the HT-106 cable (RS-232), available from AMETEK
Brookfield. The water bath requires the 225-173 cable (RS-232), which comes with the bath.
3.9 Multiple data points
Most of the viscosity and yield stress measurements are made at the quality control level and often consist of a single
data point. The test is conducted with one spindle at one speed. The data point is a useful benchmark for the go/no-
go decision in a production setting. The DVNext can be used for single point measurement.
Many fluids exhibit a characteristic change in viscosity and yield stress with a change in applied force. This non-
Newtonian flow behavior is commonly seen in paints, coatings, and food products as a decrease in viscosity as shear
rate increases or an increase in yield stress as a rotational speed increases. This behavior cannot be detected or
evaluated with the single point measurement.
Non-Newtonian flow is analyzed through the collection of viscosity data over a range of shear rates and the
generation of a graph of viscosity versus shear rate (a rheogram). This information will allow for a more complete
characterization of a fluid and may help in formulation and production of a product. The DVNext is capable of
collecting multiple data points for comprehensive analysis of flow behavior.
More information on flow behavior, shear rate and rheograms is available in our publication, "More Solutions to Sticky
Problems".
3.10 Selecting data collection
The DVNext Rheometer offers several options for data collection. The Data Collection setting is shown in Configure
M19-2101 REVISION 2.0
D V N E X T R H E O M E T E R - O P E R AT I O N A L M A N U A L
39
Advertisement
Table of Contents
