I have discovered a ground loop potential of 3.0VAC between a CNC
lathe and common ground of seperate 120v plug. The make of the CNC
are the same as the other 10 CNC's, same control, no problems there.
1) When machine is off, there is about 1.9VAC potential. Same reading
when main breaker at the panel is off for this machine.
2) When CNC is powered on, and not in E-Stop condition, the ground
loop potential is about 3.0VAC. When in E-Stop, is goes down to about
3) Checked identical machine right beside it, and there is about
0.3VAC ground potential of that machine and any other ground.
This is causing random RS232 characters on sending from the CNC, but
it is able to receive a CNC program no problem. The cable is shielded
and grounded at the computer. Ground potential readings of the cable
and the same ground near the CNC are 0.3VAC, but then measure the
cable shielded ground to the CNC, upto 3.0VAC.
Any suggestions on curing the random garbage over RS232 or fixing the
ground potential? I think fixing the ground potoential would fix the
14 years ago