[SGVLUG] Calling the brightest of cal tech and other nerds!

Donald E Gibbs dgibbs at jpl.nasa.gov
Fri Dec 22 17:06:39 PST 2006


Every time you spark the case you reset.  Okay.  The question was
asked why this happens.  Why doesn't the enclosure protect the
internals.  Well, unless the enclosure is electrically isolated,
and at least one meter from the delicate electronics, discharging
the static charge from your body is asking for trouble.  From
casual observation, power suppies tend be tied to enclosures. 
This makes for complicated analysis; lots of paths for a pulse.

Sorry I mentioned the Faraday cage; I'm not taking the bait to
start a never ending thread on some estoteric discussion.  I'll
just say that a Faraday cage was a model I tried using to
understand how ESD works but it gets complicated really fast. 

Bottom  line: if you really serious about things like this, you
do not get get within a meter of unprotected electronics if you
are not wearing a grounded wrist strap, and you never, never
spark an enclosure.

Take whatever you want from this advise.

  --Don



On Fri, Dec 22, 2006 at 03:18:56PM -0800, Christopher Smith wrote:
> Don Gibbs wrote:
> > A conventional metal case is not an electrically isolated
Faraday cage
> > (with one meter air gap).
>
> It's an aluminum case.... I'm missing how it's not enough like
a Faraday
> cage to keep the charge from spreading the party to the
components on
> the inside.

"Enough like"? I await the explanation of why a conductive
enclosure is
not *exactly* a Faraday cage.

Dustin




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