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The shielding on a cable is to avoid interference from the outside world however it is always tied directly to the GND pin. Not inside the cable itself but inside a device. Every single device I take a look at, will do this, computer/hubs, usb soundcards, usb bluetooth dongles, usb powerbanks, usb harddrives, arduino's etc.

In my perspective this make no sense at all because the shielding is now acting like a big attenna instead of a faraday cage, or am I wrong? I think this a source of noise and/or ground loop problems.

What is de reason why they doing this?

Example, when measuring resistance between shield and GND pin, it reads 0 ohm: usb connector example

Codebeat
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  • Sometimes its tied via Ferrite Beads and it will also read 0 Ohm. Also, maybe its not a good idea to refer to GND as "minus pin" in the USB context because USB also has Data plus and Data minus. – Wesley Lee Nov 01 '18 at 18:24

1 Answers1

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This question has been discussed over many entries on SE EE and elsewhere.

See

USB Shield. To ground or not to ground?
How to connect USB Connector shield?
USB 3.0 Hub shield connection

Does an overvoltage TVS for USB hot-plugging connect to shield ground?

and most elaborate answer is provided here, Structure of a usb 2.0 connector [duplicate]

It explains that the shiled serves two contradictory functions, (1) provides the path for ESD discharge, and (2) shields EMI from noise of internal digital ground. So the trade-offs must be made, depending on particular shape of USB device - handheld, grounded enclosure, etc.

Ale..chenski
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