Hi Brent and the group,
The IEC test does not come close to simulating the range of ESD that can
happen to equipment in use. It is meant to uncover common problems in systems,
not to guarantee performance. I spend a lot of time developing custom ESD
tests for people that cover problems they have been having. Often the IEC test
either cannot be applied or is totally inappropriate. Some interesting
problems have been:
- conveyor belt ESD
- jingling change ESD
- hospital ESD
- Human Body Model (from human skin as in operation of a telephone)
and many more that are quite different than the IEC model.
Doug
Brent G DeWitt wrote:
I may have not phrased my reply correctly. I definitely would
discharge to
conductive surfaces, but I would do so with the contact discharge mode. The
contact mode is more repeatable and has a faster rise time than air discharge.
I only meant to say that after doing contact discharge evaluation of
conductive surfaces, I wouldn’t also apply air discharge to the same points.
Does that make more sense?
Respectfully,
Brent
From: Fred Townsend [mailto:[email protected]]
Sent: Monday, May 18, 2009 7:20 PM
To: Brent DeWitt
Cc: Bill Owsley; [email protected]
Subject: Re: [PSES] ESD testing
Brent: I would have to ask on what basis you would exclude conductive
surfaces? My experience has been grounding defects were exposed by conductive
discharge and as such it was a very valuable engineering tool.
Fred Townsend
Brent DeWitt wrote:
Ian,
I have always been of the opinion that it is not required to do air
discharge
to conductive surfaces. That said, my current employer has written internal
standards to include air discharge to conductive surfaces. I'll be
interested to see where this thread leads.
Brent DeWitt
-----Original Message-----
From: Bill Owsley
Sent: May 18, 2009 12:27 PM
To: [email protected]
Subject: Re: [PSES] ESD testing
The fun part of air discharges to insulating surfaces is that things are not
always what they appear to be. The air discharge can find a way around lots
of apparent insulation to find the nearest conductor and insert all sorts of
havoc in the system.
- Bill
Indecision may or may not be the problem.
--- On Mon, 5/18/09, Gordon,Ian <[email protected]>
<mailto:[email protected]> wrote:
From: Gordon,Ian <[email protected]>
<mailto:[email protected]>
Subject: ESD testing
To: "IEEE EMC & SAFETY PSTC" <[email protected]> <mailto:[email protected]>
List-Post: [email protected]
List-Post: [email protected]
List-Post: [email protected]
Date: Monday, May 18, 2009, 7:09 AM
All
Is it necessary to apply both air & contact discharges to equipment
given the following?:
Looking at 61000-4-2 I believe the critical part is the first paragraph
of section 7 ".Test set-up".
.....application of discharges to the EUT in the following manner:
a) contact discharge to the conductive surfaces and coupling planes;
b) air discharge at insulating surfaces.
it does not say for air discharge at insulating AND conductive surfaces.
The table in section. 8.3.1 is just for conductors but is essentially a
restatement of the above.
I cannot see any other part of the spec that implies the opposite.
Ian Gordon
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