Hood,
OEMLed(16) did the trick. I Found this solution works well. I used an ElseIf and posted the message in the status window. That way the process is automatically terminated on this error condition. Added it as follows:
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If GetOemLed (825) <> 0 Then 'Check to see if the probe is already grounded or faulty
Code "(Probe is grounded, check clearance and try again)"
ElseIf GetOemLed (16) <> 0 Then 'Warning Wrong Coordinate system
Code "(Center Finder Error: Exit Machine Coordinate Mode)"
Else
(Body of the code)
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I added a second pass at finding the center of the X axis, because I didn't trust the probe to give me good results if it starts out next to the Y edge of a hole. Once the near X axis center is found, the probability of a clean touch goes way up. The process now searches for X, then Y, then X again, done. On several practice runs, I noticed that the X center moved a few thousandths on the second pass, but never by more than 0.001 on a search starting from the near center of the circle. This is well within the slop of the CNC machine.
Thanks,
Bill