You write that with your SKP5050 package you supply the optical/TFT monitor arrangement to monitor tip-to-sample displacement and tip positioning on the sample. How are these functions achieved in other, not SKP5050 packages?
The TFT monitor/camera arrangement can be configured to watch the probe position on the sample or in higher magnification the separation of the tip and sample. On some surfaces this can be difficult to see by eye. Also with our smaller tips, e.g. 50 microns diameter, camera positioning is necessary. Note that this is used for initial tip position and as a general visual check to see where the tip is currently on the sample, for instance on several of our in-house systems the PC is separate for the optical table or desktop supporting the KP/SKP/RHC-KP.
After initial macro-positioning beside the equipment reverting to computer control of tip to sample spacing is far more accurate. There is an option to keep sample to tip spacing constant to within 1 micron during scanning and this is done by monitoring the Kelvin probe signal and automatically adjusting the sample height to the vibrating tip.
In non-motorised system it is possible to use a DC Offset applied to the voice coil. However the motorised systems give 25 mm of height control and the DC Offset only about 0.1 - 0.3 mm.