Ch. 4. Tutorial: AC Mode in Air, Std. Scanner Sec. 4.4. Imaging
Nomenclature
In the previous image the tip is not following the surface. As the blue trace
shows (left to right), the tip seems to climb up out of the pits of the
calibration grating quite nicely (the left edge of each pit is quite sharp) but
then it descends back into the next pit along a relatively gentle slope. During
this descent the tip actually “flies through the air” while it is completely
un-deflected, a bit like a hang glider running off a cliff. The lateral motion of
the tip simply marches on as dictated by the XY scan pattern. The feedback
control algorithm is simply not aggressive enough to bring the tip back down
to the bottom of the pit. Such behavior is commonly called parachuting or
poor tracking.
Hamster
The next steps will go into the details of strategies for tuning parameters in
the main panel. Use the arrow clickers (to right of variable fields) to adjust
parameters, rather than typing the values in. Alternatively, you can fine-tune
the parameters using the ‘Hamster’ wheel on the front of the controller. Any
parameter with a radio button next to it can be changed during a scan when it
is activated (looks like black/ green dot in circle) with the ‘Hamster’. The
Hamster gives "digital control with analog feel". On the MFP-3D AFM
controller the toggle switch to the left of the ‘Hamster’ allows you to toggle
between radio buttons in the panel. On the ARC2 SPM controller the outer
‘Hamster’ ring performs this function. This tactile experience lets you
concentrate on the image while tuning parameters.
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