Force Imaging
Force Calibration Control Panels and Menus
188
MultiMode SPM Instruction Manual
Rev. B
11.3.5 Scan Mode Panel (Advanced Mode Only)
Trigger Mode
The
Scan Mode
panel allows you to use various triggers when obtaining
Force Plot
and
Force
Volume
plots. The idea of triggering 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
fi
xed point (
Absolute
).
Figure 11.3b
Absolute and Relative Triggers
show the effect of drift on each of the two trigger types. The plot series
utilizes a
Relative
trigger and maintains force at a constant
level de
fi
ned 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 unde
fl
ected. As illustrated, the total force is
maintained, even as the system drifts.
The plot series on the left side of
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
Setpoint
values.
Trigger Channel
This parameter de
fi
nes the channel to watch to determine when to reverse the ramp.
Total Force
