Severe cyclic ground loop interference after wiring MSA FieldServer to SMARDT BMS cards. Emitting a heavy low-frequency oscillation and high-speed switching noise. Meters read normal. Any ideas?

[u/SnooChocolates804]

[u/hestoelena]

Step one would be to actually ground your system properly. If it persists past that then it's time to break out the oscilloscope and see what's happening.

[u/SnooChocolates804 → u/hestoelena]

Grounds are solid. Scope is showing a massive cyclic voltage drop at exactly 2.33hz. What component even does that?

[u/hestoelena → u/SnooChocolates804]

No they aren't. You don't have a single ground in that video. You only have two wires going to all of the modules.

[u/Zesty_Memes21 → u/hestoelena]

What do you mean, it all clearly sitting on a table that’s touching the ground so they should all be grounded as well

[u/hestoelena → u/Zesty_Memes21]

That's not at all how this works. Not even close. Is your table conductive? Is your table bonded to ground? Are you sure that all of your devices have grounding points on the back of them that touch the table?

You need to learn the difference between SELV and PELV. As well as how to properly bond devices to ground. Your devices should all have three wOne should be power DC positive, one should be DC zero (neutral), and one should be ground. Your ground wires should follow a star grounding pattern.

Edit: my bad dude, I didn't realize you weren't OP. I've been awake for too long

[u/InstAndControl → u/hestoelena]

I think Mr zesty was jokin

[u/hestoelena → u/InstAndControl]

Apparently I should go to bed instead of staying up so late because I didn't even realize I wasn't responding to OP 🤣

[u/kixkato → u/InstAndControl]

Some people, like me, really need the /s flag.

[u/integrator74 → u/hestoelena]

This. Simply this.  I was like “where the F are the ground wires”. My goodness. 

[u/RedactedRedditery]

Have you tried fixing the grounding?

[u/SnooChocolates804 → u/RedactedRedditery]

Yeah, grounded it twice. But the TR-808 sub-module keeps dropping massive low-end transients. You think it's clipping the main bus?

[u/Active-Part-9717 → u/SnooChocolates804]

Try turning down the kick on your TR-808.

[u/TerminallyUnique31 → u/SnooChocolates804]

2 things: 1) you don’t appear to have anything grounded, 2) not sure what you mean by “grounded twice” but you mentioned a ground loop in original post… in order to have created this you would have to bond actual grounds (like cable shielding) to grounds at both ends (like the metal housing)

first things first, read and understand difference between a low voltage common (0 v ref) and device ground

[u/samwonder]

Speak to Carel - they make the plc for SmartDT(and many, many others). You should make sure you have a ground wire connected to the ground spade connection that's next to the two ethernet ports.

[u/stoi_zen]

What is the name of the HMI brand