Re: Chassis -- shielding and ground

On Oct 25, 9:49 am, mkr5000 <miker...@xxxxxxxxx> wrote:
Went back and read the answers carefully.....

For electrostatic fields -- yes?

For electromagnetic -- no?  (or not necessarily)?

For electromagnetic, aluminum is a poor choice compared to steel (plus
zinc and some others?)

For EM, depends on frequency. My induction heater lives inside a box
of 0.093" aluminum. Nothing is getting through that (although it
would be hard to measure, since I've got the work coil blasting
nearby, anyway ;-) ). It runs at 20-100kHz. Aluminum of that size
isn't even too bad at 60Hz, IIRC, though mild steel will do better.

Zinc is almost as conductive as aluminum, and a lot heavier, so if you
need something mechanically and electrically dead, a diecast zinc
sacophagus will do an excellent job.

Static magnetic fields aren't usually a problem, but where they are
(e.g., CRT scope?), mu metal shields are excellent.

As for grounding, the ground line is for protection only. It often
carries noise, which is why it's such an awful problem to hook up
grounded equipment. If you have something sensitive, you're better
off grounding the case to the circuit, leaving it isolated from the
line.

Tim
.

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