Force Imaging
Force Calibration (Contact Mode AFM)
Rev. B
MultiMode SPM Instruction Manual
193
Figure 11.4b
False Engagement (G Scanner)
Motor Control
Motor Control
>
Tip Up
and
Tip Down
buttons provide coarse adjustment of
Z center
voltage.
With these buttons the SPM head moves vertically. The feedback loop causes the Z piezo to adjust
to compensate for the head movement. If you use
Tip Up
, the Z piezo extends. If you use
Tip
Down
, the Z piezo retracts.
Note:
The
Step Motor
function is generally used only when the scanning range of the
Z piezo is exceeded or when it is necessary to position a force measurement in
the center of the scanner range. Because the Z-axis leadscrew has some
backlash, it may be necessary to rotate the leadscrew several turns by clicking
on the
Tip Up
or
Tip Down
buttons before obtaining movement.
Adjust Photodiode
In an analogous manner, you can use the photodiode positioner as a coarse adjustment for
Setpoint
voltage. Changing the laser beam position on the photodiode by rotating the photodiode adjustment
knobs shifts the force curve on the graph. Rotating the top photodiode adjustment knob counter-
clockwise shifts the curve up, just as decreasing the
Setpoint
parameter shifts the curve up.
Conversely, rotating the top photodiode adjustment knob clockwise moves the curve down.
Tip
Deflection
0.48 V/div
Z Position - 9.27 V/div
Setpoint
Retracting
Extending
Possible False Engage Points
