I am working on placing my machine in an enclosure and have discovered that I have a ground loop between my control cabinet and my computer/monitor. By using a continuity tester I am able to verify a connection between the negative terminal on my Black Box and the equipment grounding conductor of the power supply. This connection is only present when I have a second monitor connected to my laptop. So the path goes like this, power cord from monitor to HDMI to computer to USB to black box. Can any one recommend an isolator or another solution that will help with this?
Before you consider "isolating" a part of the loop, rather see if you can fix the short. DC GND and AC Earth should not be connected together. Its also dangerous. Isolating, say, USB - addresses the symptom, but not the cause.
Sorry if my post was not clear, the connection is in my second monitor. The monitor is connecting the dc ground to the ac equipment ground or earth. I have verified this with a continuity tester.
Then I would consider replacing the monitor. Any device that shorts DC GND to AC Earth is dangerous. If an AC Earth fault occurs (somewhere in the house a wire in an appliance chaffs through, shorts on the chassis) the shared Earth bus is momentarily at mains voltage until it trips. In that time, this short dumps a big mains spike into your low voltage side of the electronics, and kills it. Simplified of course, but hopefully you understand why we recommend, rather eliminating components like that.
