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Question about shielding

I know some things about how to keep RF and ESD out of a circuit... and I'm confused about some others.

I understand from this thread: "Ferrite on audio leads passing near PC?" that for low frequencies it is sometimes advantageous to only connect the shield of a cable at one end. And connect different boxes' grounds in a star formation. But when is it a good idea to connect it at both?

Up to now I'd thought it was always best to connect the shield at BOTH ends unless there were significant ground loops, to get a Faraday cage which keeps out RF and, if the shield is good enough, probably ESD too. Also I'd heard that multiple points of grounding of a PCB helps to avoid ringing.

Perhaps I am getting confused between signals going down a single core coax cable and multicore shielded cable? Or does it just depend on the particular installation, geometry, types of signal, strength of interfering signal?

Thanks in advance for any clarification,

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Nemo
Reply to
Nemo
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Connecting coax shields to chassis at both ends is usually best for RF and ESD immunity. And with so many RF devices around these days, RF shielding is important.

As far as low frequencies go, if you don't connect the shield on one end, the only signal return path is the AC power wiring, which is a lot worse than the coax shield.

There are common-mode chokes that can be used to keep 60 Hz loops out of single-ended audio and video circuits. They are a lot like ferrites, but have much, much more added inductance.

Go differential for serious between-box signal integrity.

John

Reply to
John Larkin

Thank you for the responses,

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Nemo
Reply to
Nemo

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