© ICSPI Corp. 2007-2021
nGauge AFM User Manual 2.0
33
5.7.2.2.
Z Fine PGA
The
Z Fine PGA
sets the physical vertical range of the Z scanner. The default value is 20. The
Z Fine PGA can be changed in the Advanced Menu button in the top right of the screen.
Note
: the Z Fine PGA is different from the Z Fine DAC. The Z Fine DAC is not a control: it is an
indicator. More information is available in Section 8.3 Menu Button Advanced Controls.
Increasing the Z Fine PGA will increase the Z scanner range but decrease the resolution.
Increasing the Z Fine PGA is recommended for scanning samples with large peak-to-valley
distances in topography (on the micrometer scale).
Lowering the Z Fine PGA will provide higher resolution, but it will decrease the Z range that the
scanner can move. In other words, lowering the Z Fine PGA makes the tip more prone to
damage, as the Z scanner can more easily go out of range.
Before the Z Fine PGA is decreased, it is recommended that the Leveling is set to an
appropriate value.
Large vertical range
Z Fine PGA = 50
For measuring tall features
(>5 µm). Low vertical
resolution.
Standard vertical range
Z Fine PGA = 20
Default. Ideal for general
purpose imaging
Small vertical range
Z Fine PGA = 5
Good for measuring small
features (<20 nm). Highest
resolution, but the tip can be
damaged more easily.
5.8.
Improving Performance
There are several parameters that can be controlled to improve imaging performance. The
parameters are interrelated.
5.8.1.
Time Spent at Each Point
The
Time spent at each point
is the number of microseconds that the tip will dwell at each
data point. As you decrease this value, the scan speed will increase and the controller will have
less time to track the sample topography, possibly leading to poor image results. The default
