Re: [PSES] ESD question

Cortland Richmond Sun, 07 Jan 2018 08:18:51 -0800

Title: Re: [PSES] ESD question

I was working at Tandy Computers, and the EMC department was often blamed for strange occurrences. We perforce had to become experts at demonstrating causes not within our control, and the software compatibility lab with its bare motherboards was one case where I was able to use very basic physics to identify the separation of charges and pushing back before lunch as locking the systems up.

As far as I know, no one EVER commented on the wet bottoms staff in that room had to accept.

Other problems occurred from time to time and perhaps I should write them up for Banana Skins.

Cortland Richmond

-----Original Message-----
From: Ken Javor
Sent: Jan 7, 2018 10:50 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] ESD question

In Doug Smith’s demo of a spark gap and charged paper cup, there was movement of charge induced in the point closest the cup, and that generated a potential difference across the points. So even though the total amount of charge may have been static, there was a change in local charge and hence potential difference across the points.

Since we are being philosophical here, it seems the same can be said of any ESD event, if the picture is big enough. That is, walking across a rug, petting a cat, or whatever activity “generates” the charge in fact doesn't generate any charge, it simply separates it and moves it around. Enough charge separation, we get a potential difference, electric field and eventual discharge.

So says Coulomb.

Ken Javor
Phone: (256) 650-5261

From: John Woodgate <j...@woodjohn.uk>
Reply-To: John Woodgate <j...@woodjohn.uk>
Date: Sun, 7 Jan 2018 15:00:00 +0000
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] ESD question



If the charge is still building up, the field is not static in the region close to whatever the charge is building up on. Just a philosophical point.

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK

On 2018-01-07 14:28, Ken Javor wrote:

Re: [PSES] ESD question Cortland: Faraday Law purely inductive coupling from an ESD event doesn't cause potentials that breakdown dielectric barriers; it induces potentials that cause bit shifts. But to answer John Woodgate’s question literally, enough charge buildup with some capacitance eventually yields a potential high enough to cause dielectric breakdown. Since that is basic, I assume I misinterpreted his post.

Ken Javor
Phone: (256) 650-5261

From: Cortland Richmond <k...@earthlink.net> <mailto:k...@earthlink.net>
Reply-To: Cortland Richmond <k...@earthlink.net> <mailto:k...@earthlink.net>
Date: Sun, 7 Jan 2018 06:23:07 -0500
To: <EMC-PSTC@LISTSERV.IEEE.ORG> <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] ESD question

Induction; I once saw motherboard testers shut down systems under test by just walking away from the work table at lunchtime. Sliding across the cloth chair seats generated a charge, and walking away biased the motherboards and shut everything down.

(They didn't have the funds for antistatic protection – so for a few months, we had them spraying the chairs with a solution of water and detergent. You could tell who worked there because the seats of their pants were wet...)

Cortland Richmond


-----Original Message-----
From: John Woodgate
Sent: Jan 7, 2018 4:10 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] ESD question



Philosophical issue there. If the field is really static, what changed to cause the spark to happen when it did, rather than at some other time? (A cosmic ray would breach the stasis.)


John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk <http://www.woodjohn.uk> <http://www.woodjohn.uk>
Rayleigh, Essex UK

On 2018-01-07 03:37, Doug Smith wrote:




Hi Ed and Ken,

  An ESD event can be produced without any direct addition of charge. It only takes an E field and two conductors near each other as in:

  http://emcesd.com/tt2001/tt060101.htm

  http://emcesd.com/tt2001/tt050101.htm <http://emcesd.com/tt2001/tt060101.htm>

  Unobserved discharge not needed and generally is not involved with these type of events. Just a static E field will induce a spark.




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Re: [PSES] ESD question

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