Re: [SI-LIST] : ESD Smocks

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From: Paul Taddonio (ptaddoni@nortelnetworks.com)
Date: Wed Dec 20 2000 - 07:30:59 PST


It sounds like a gimmick. The human body is already plenty conductive (its the
insulation on the bottom of our footwear that causes the body to build up
charge). Adding a conductive cloth over an already conductive body sounds
useless.

At 09:59 AM 12/20/00 -0500, Michael Nudelman wrote:
>Hail to you, people that know electricity.
>
>I have unrelated to SI question. And this question does not come from my
>ancient animosity to ESD smocks. It comes but from the desire for pure
>knowledge (and some distrust for businesses mongering ESD equipment).
>
>Now, somebody please explain me the principle of the ESD smock's
>operation. It is a gown, laced through by carbon fibers, forming a cage.
>(St. Mike Faraday is smiling in heaven reading this, I'm sure).
>
>As I remember from my Electricity course, any Faraday-cage-like device
>(hollow metal object) is intended to protect inside from outside (a
>static field inside the object is always zero if all the charges are
>outside).
>However any charge that is inside the object, upon touching the inner
>surface will transfer ALL of its charge to the outside surface of the
>object, thus
>itself loosing 100% of the charge and the charge being distributed
>evenly on the outside surface of the object. The object in our case is
>the smock.
>
>BTW, the Van-de-Graaf generator (the one capable of developing few
>million volts potential) works exactly on the same principle.
>
>For the smocks to work we need conductive floors and everybody wearing
>straps. Otherwise, smocks are potentially harmfull. If you touch
>something with it while not grounded, you may actually zap some poor
>unsuspecting FET or a co-worker (unless he deserves it).
>
>(And as I know, lots of companies do not have those floors. And ESD
>businesses do not really insist on them - otherwise they would loose
>some business, admitting, that the smock itself is not the remedy).
>
>Unless there is some gimmick to the smock that I do not know of.
>
>Anybody can explain this ... phenomenon?
>
>Mike.
>
>
>
>
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>

--------------------------------------------
N. Paul Taddonio

Nortel Networks, Optical Ethernet Switching
600 Tech Park, Billerica, MA 01821, (mailstop E65-60-203)
phone: 978-288-4611 fax: 978-288-0620
email: ptaddoni@nortelnetworks.com

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