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NS3 Contact Mode Engage Problem with MSNL-C Probe

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Top 200 Contributor
4 Posts
Points 47
Rob Sleezer posted on Thu, Jan 9 2014 10:43 AM

We are noticing an engage behavior problem when using a soft cantilever (Bruker MSNL-C, f0 = 6-10 kHz, k = 0.01 N/m) on a Dimension 3000 system, NS3 controller in contact mode, running v.5.x software: There is an audible sound as if your driving a cantilever with the z-piezo, e.g. using a wet mode contact holder, when the system attempts to engage the surface .  


Using the SAM to examine the z piezo voltage shows a 10V peak to peak signal and a 5V pk-pk deflection signal, both at frequencies of approximately 6.7kHz.


By raising the set-point sufficiently high enough the problem disappeared.  Switching cantilevers (stiffer probe) caused the problem to disappear and we could not replicate the behavior by reducing the set point.



The behavior of the set-point indicates there is some kind of feedback occurring to the z-piezo, but we do not know what this could be.  Any help explaining and understanding this would be greatly appreciated.

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Top 50 Contributor
20 Posts
Points 220

Check the "minimum engage gain" setting in the "other controls" panel - I believe the contact mode engage uses whichever is higher out of the integral gain set in the feedback panel or the minimum engage gain, so it may be that your minimum engage gain is set too high and causing oscillation of the Z piezo.

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