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I have been told that there is a ground loop in this diagram especially via USB_GND, Power-, GND. But I don't understand what that means. All the power supplies are SMPS. Can someone draw the loop on my diagram below:

enter image description here

Arduino's digital output above is connected to the digital input of the DAQ board.

I have been told there is ground loop from several forums but I'm not able to verify the loop. Im stuck at that point, I would be glad if someone can draw such ground loop so I can proceed.

user1245
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  • Are the SMPSs isolated? – Jack B Nov 18 '18 at 20:52
  • Yes It seems like they are one of them here https://www.alliedelec.com/m/d/b68e2ad13f6e9ec8a80045abded1c210.pdf The other also have opto isoaltion in feedback so I guess they are isolated – user1245 Nov 18 '18 at 20:58
  • The other is https://www.cdiweb.com/datasheets/meanwell/rs-25.pdf – user1245 Nov 18 '18 at 20:59
  • I think they mean a loop which pick up EMI. Because star ground was suggested. – user1245 Nov 18 '18 at 21:00
  • "I have been told there is ground loop from several forums" Please edit the question and add links to the relevant threads in those forums. That will help to avoid wasted effort here, where readers make suggestions already made elsewhere. Thanks. – SamGibson Nov 18 '18 at 21:18
  • @SamGibson here https://electronics.stackexchange.com/questions/405508/what-could-be-causing-this-interference-and-how-to-eliminate-it – user1245 Nov 18 '18 at 21:23
  • @user164567 - Thanks for that, but you said several forums, so that implies more than one place. Are there others? If not, then I suggest you replace the phrase "several forums" with that link - and preferably link to the specific comment claiming there's a ground loop (which I think is this one https://electronics.stackexchange.com/questions/405508/what-could-be-causing-this-interference-and-how-to-eliminate-it#comment1003264_405508). Then readers will see clearly where you are getting that suggestion from. Thanks and good luck with the problem! – SamGibson Nov 18 '18 at 21:43
  • @SamGibson No I want to keep that private didnt get permission from the people who put their names. sorry – user1245 Nov 18 '18 at 21:45
  • @user164567 - "I want to keep that private didnt get permission from the people who put their names. sorry" Oh. :-( If you are referring to a public forum, then there can't be any expectation of privacy, by the people who post there. And if it's not a public forum, you could copy & paste the information (or your own synopsis of it) without their names. It's a shame that information is being hidden, and I'm sure you can see how hiding information may result in you not getting the best answers here. But it's your choice, so I'll stop here. :-( Good luck. – SamGibson Nov 18 '18 at 21:59
  • Adding link to this new, related question, so that readers here can be aware of it. – SamGibson Nov 18 '18 at 22:44

2 Answers2

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It means you have 2 ground connections, one in the PC and an other in the daq power plug, if the pc and the daq are spaced there may be a voltage difference between those grounding points and current may flow, that current can be high enough to the point of burning the cables, and in the case there ground wire between the pc and the daq breaks the voltage can destroy the usb ports for example, that is assuming the SMPS output is not isolated from ground or that the ground from the board is not connected to chassis, otherwisepossible ground loop, then there is no ground loop

diegogmx
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  • One of the SMPS is this https://www.alliedelec.com/m/d/b68e2ad13f6e9ec8a80045abded1c210.pdf And the other is https://www.cdiweb.com/datasheets/meanwell/rs-25.pdf – user1245 Nov 18 '18 at 20:59
  • I think they mean a loop which pick up EMI. Because star ground was suggested. – user1245 Nov 18 '18 at 21:00
  • Here actual photo of the diagram https://i.stack.imgur.com/dF3jE.jpg from my previous question – user1245 Nov 18 '18 at 21:03
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enter image description hereIn your schematic the ground loop is already there. it is nothing but connecting all ground together for common reference point.

Electron
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