For my server I will use a PIKVM, which is a Raspberry Pi 3/4 used as KVM. Since the Raspberry needs an internet connection, I assembled a pass-through Ethernet port onto the chassis, which will then be connected to the Raspberry:

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As this jack is made of metal, it has contact to the chassis, thus it is connected to the ground of the PSU of the server.

Can this be a problem? Would it make sense to isolate it from the chassis (e.g. using 3D printed TPU underlayments), at least in case the Raspberry will get its power from the original Micro-USB power unit?

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    \$\begingroup\$ Welcome! Ethernet is transformer coupled so the signals are separated from chassis ground. You probably don’t need to do anything. Are you expecting any problems? \$\endgroup\$
    – winny
    Feb 6 at 0:11
  • \$\begingroup\$ Thanks for the edit, I love accuracy! Well, I don't absolutely know if I can expect problems, but I assumed that the wires of an Ethernet cable are not connected to ground and that the only reason for grounding the jacks (such as on the motherboard) is to drain any interferences to earth. So normally I would not expect problems from that perspective, but it is safer for me to verify that. \$\endgroup\$ Feb 6 at 0:17
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    \$\begingroup\$ That is the proper connection for an overall shield on a cable carrying high speed digital signals. Tie the cable shield to the metal backshell of the connector around the entire periphery (360 deg) of the cable, and connect the backshell to the chassis. \$\endgroup\$
    – SteveSh
    Feb 6 at 0:20
  • \$\begingroup\$ The question is more like how did you assemble the connector. Did you use shielded cable and connect the shield as in the installation instructions, or if you used a non-shielded cable or did not connect it? Mounting the metal connector shell directly to metal chassis is usually the correct thing to do, as it may not be connected to anything else, it might even have separate pass-through for cable shield. Hard to see. Which exact connector model that is? \$\endgroup\$
    – Justme
    Feb 6 at 5:39
  • \$\begingroup\$ The RJ45 connector is the Neutrik NE8FDP. The cables I usually use are shielded cables - however, I believe - but I am not 100% sure - that in the datacenter they will use unshielded patch cables. Nonetheless, if shielded or not, not a single wire of the Ethernet connection is connected to the shield, right? In that case it should not cause any troubles by exclusively using shielded cables. \$\endgroup\$ Feb 6 at 14:59

1 Answer 1


Use an unshielded patch cable to connect to the back side of that socket and there will be no ground loop problems, because the signal lines are transformer coupled.

Would it make sense to isolate it from the chassis

No, when shielded cables are used the shield should connect to the appliance shell.

  • \$\begingroup\$ Thus unshielded inside to isolate the Raspberry from it, but shielded outside, correct? What could a ground loop on Ethernet lead to? Is the Raspberry actually grounded? I wonder because it only gets plus (+) and minus (-) DC and has no third wire for earth, other than the PSU which is grounded to earth. \$\endgroup\$ Feb 6 at 0:36
  • \$\begingroup\$ I'm not an expert on choosing ethernet cables, but I note that the main board's ethernet socket will also ground the shield if a shielded cable is used there, so in a circumstance where a shielded cable is suited for one it would also work for the other. \$\endgroup\$ Feb 6 at 0:49
  • \$\begingroup\$ @Tintenfisch You have the Raspberry Pi, you can measure if the connector shell is grounded or floating. A typical PC will anyway connect the PC metal chassis to circuit common ground anyway, sometimes even the Ethernet connector shields. You can measure that too if you want to find it out. \$\endgroup\$
    – Justme
    Feb 6 at 5:56

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