hi there.
you can see the local variables being controlled by the inputs on the top part of the block diagram. as we have not calibrated the system, the range of movement is somewhat proportional to the change in voltage applied to each crystal.
therefore
if one thinks of a 64 by 64 pixel picture and would like the X and Y piezos to scan through 5V worth of distance each, each pixel corresponds to 5/64 V of displacement
swngiam would like offer a brief into to STM:
STM or scanning tunneling microscopy is a non-optical magnification
technique which at best gives atomic resolution electrically conductive
surface.
by quantum theory, a a small magnitude (think nanoAmperes) of
"tunneling current" tunnels through a very small physical gap between
the surface-of-study and an atomically sharp tip when a potential
differnece is applied between them.
a feedback logic enables the tip to respond to changes in surface
topography when you raster the tip in the XY position; by maintaining a
constant tunneling current. when distance increase, tunneling current
decreases, voltage across Z-piezo is increased to maintain the original
tunneling current
since the tunneling current changes (exponentially) with tip-surface
distance, if one plots out the Z-piezo's voltage (Analog In, controlled
by the feedback mechanism) one gets 3D surface data.
HOWEVER, the problem with my VI is its movement are all sudden as the transition from point to point is not smooth.
the danger is that the change in displacement (for eg in the X
direction) is too fast for the feedback to "safely" avoid large
topographic changes. if the tip comes into physical contact with the
surface henceforth, it would 'crash', rendering the tip un-useable.
i have employed the DAQ express VI to feed in my voltage data and read my voltage data; sure tell-tale signs of newbie-ness here.
