Nanosurf easyScan 2 AFM, Operating Instructions Manual

Page: 103 / 164

T
HE
Z-C
ONTROLLER
P
ANEL
103
of 70% is used, the Z-Controller will move the tip closer to the sample until
the vibration amplitude has decreased to 70% of the vibration amplitude
far away from the sample.
Loop-Gain (Easy)
The speed of the Z-Controller. If the gain is too low, the Z-Controller will
not follow the surface fast enough. Thus, the image will not be as sharp as
it could be. If the gain is too high, the Z-Controller will overshoot and may
start to oscillate. Thus, the image will contain many measurement artifacts.
P-Gain (Standard, Advanced)
The strength of the Z-Controller reaction that is proportional to the error
signal. Increasing the P-Gain decreases the error signal.
I-Gain (Standard, Advanced):
The strength of the Z-Controller reaction that is proportional to the inte-
gral of the error signal. Increasing the I-Gain decreases the error signal over
time. It is the least sensitive to noise, and usually the dominant contributor
Z- Controller
Set point
Topography
Error
Signal
+
-
+
Control Signal
(Tip Current,
Deflection,
Amplitude, ...)
1..16x
Error
Range
P-Gain
D-Gain
I-Gain
dt
d
dt
+
+