Section 4: Experimental Tutorials
has equilibrated in the Pre-stirring mode you may want a closer look at the data, so click on the
Auto-View 1
button. This will put the current data point at the center of the graph with a Y-axis
full scale of 0.1.
You may notice that when the graph first appears in Origin, the DP data display box in
VPViewer’s main window has the values displayed in red. Once VPViewer determines that the
cell has equilibrated in the Pre-stirring mode, the data display will turn to green. This means that
the cell is ready to enter the stirring mode of equilibration. Since
Auto Start
in the
ITC
Equilibration Options
group was enabled in the
ITC Controls
window, VPViewer will
automatically start the stirring and apply power to the reference cell, moving on to the next state
of the equilibration process. If this option was not selected the DP value that turned green
becomes a button that will move the instrument to the next state when it is selected.
When VPViewer starts the
Final Baseline Equilibration
it starts the stirring and applies power
to the reference cell. The amount of power applied to the reference cell is determined by what
you entered into the
Baseline Position (uCal/sec)
text box located in
ITC Controls
window.
For this tutorial we entered 5 for the Baseline Position, you may see that there may be an initial
decrease in the DP power (due to the added frictional energy in stirring), but then the DP values
will increase because of the power applied to the reference which forces the feedback system to
apply power to the sample cell to compensate and maintain a temperature balance. The effect of
this heat disturbance will take a few minutes for a new equilibration level with the final DP
values being close to 5. Select the
Rescale to Show All
button and you will see a graph similar to
the above.
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