The Mode panel allows you to use various triggers when obtaining Force Plot and Force Volume plots. The idea of triggering is simple: it limits the total amount of force exerted by the tip upon the sample. Depending upon which trigger you use and how it is set, you may operate the trigger independent of drift (Relative) or at some arbitrarily fixed point (Absolute).
The plots above show the effect of drift on each of the two trigger types. The plot series shown on the left uses a Relative trigger and maintains force at a constant level defined by the Trig threshold parameter. The Relative trigger threshold is relative to the data at the right of the plot where the cantilever is typically undeflected. As illustrated, the total force is maintained, even as the system drifts.
The plot series shown on the right uses an Absolute trigger. Notice that as the system drifts (plot moves slowly downward), total force increases. Drift may be due to mechanical causes, or due to thermal effects on the cantilever. An Absolute trigger permits the total force to be set using values.
Trigger Mode
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