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Old 09-26-2015, 12:26 AM   #2084 (permalink)
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Originally Posted by e*clipse View Post
Oh, I may see something here, regarding your shielding.

Generally, you don't want to connect the shield to both the main circuit board's ground and the "satellite" circuit boards ground. The shield should only connect to the main circuit board's ground. Otherwise, you can get current loops that are separate (and dynamic) from the normal ground.

This point was emphasized in my EMI class, as well as the instructions for shielding the inputs on my Sumitomo VFD.

Hope this helps,

The 'shield' was connected to the negative on the power supply. 'Both sides' referred to the power supply side and the encoder side of my circuit board with the voltage divider. There was no termination of the shield on the encoder side.

Like I said - the noise was very bad on the scope. I wondered if the scope probes were acting as an antenna - not the aluminum foil - but the encoder signal was not making it to the AC Controller board in a usable way.
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