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If I have shielded cables, jacks and plugs and I ground the shielding properly, then should I use shielded plugs at the computer's site too? I mean if I do so, then the shielding will be connected to the motherboard or to the case, which I am not sure I want...

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  • \$\begingroup\$ Welcome to the site. Please realise this is not a free design house, homework-answering service or an on-line technical encyclopedia, copied out to you on demand. People will help you take the next step if your question shows you've done as much as you possibly could on your own - which yours doesn't, I'm afraid. Please edit your question and greatly improve it, showing your work and findings in detail.The better the quality of your question, the better the quality of the answers you will attract. Again, a warm welcome to the site. \$\endgroup\$
    – TonyM
    Feb 3, 2019 at 13:00

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Shields are tricky, as the likelihood of introducing a ground loop when using them is rather high. This could lead to unpredictable performance issues.

Shields are optional on Ethernet, and the connection itself is galvanically isolated from the PC. The interface can tolerate more than 1kV difference between both sides and the cable common-mode is terminated, thus reducing EMI generated/accepted interference.

Common practice is to ground the shield only on one side of the connection, thus providing a path to ground while avoiding the potential ground loop.

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  • \$\begingroup\$ I need a more direct answer. Can a connector like this: au.rs-online.com/web/p/rj45-connectors/3646390 cause a ground loop by connecting the shielding to an electric device, e.g. a computer, switch, etc? Or can it damage the device? I am asking because I have patch cables with these shielded connectors on both ends. As far as I understand the concept it would be a lot better to have shielded connectors only on that end, which connects to the wall cable. I can connect the shielding of the wall cables to the rack, where I can ground the shielding on a single point and avoid ground loops \$\endgroup\$
    – inf3rno
    Jan 31, 2019 at 6:40
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Shielding either protects the inner conductor from external fields or prevents the cable from radiating radio emissions. Another use for shielding is to shield the cables from static shock from a user or being dragged on the floor (which generates considerable charge). Most digital signals don't need shielding because they have ways of minimizing noise. For example, Ethernet, USB, SATA and many other buses use differential signaling to minimize noise. And most employ CRC or some kind of error correction/detection to reduce noise further.

For the cables that do has shields such as USB, the shield is tied to the motherboards ground or chassis ground. The shield only needs to be tied to a ground, and the closer to the cable input the better to minimize inductance that may prevent the shield from being effective at high frequencies. Cables that could experience large static shocks (from humans) should have the shield tied to chassis ground to route the current away from the products ground plane.

There isn't a 'best way' with electromagnetic compatibility engineering because it really depends on the application.

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