Hi Ram,
Thanks for the reply. Having helped develop this standard for many years I am
aware of the issues you bring up. Your treatment is a good tutorial on the
problems of ESD testing in any event and good to get out to the group.
I was surprised to see such a large difference in the initial spike on the
Teseq simulator compared to the MiniZap and Onyx simulators. Clearly the Teseq
we had rented had a problem. It does not look like it would meet the
requirements of 61000-4-2 to me.
I am sure these rented machines lead a hard life, but I would expect the
rental companies to do a quick waveform check (not a real calibration) before
sending the machines out again, sort of like the test I posted. Such a check
only takes a couple of minutes, less if done as part of an incoming inspection
when the simulator comes back from rental.
Doug
On 12/9/10 5:46 PM, Ram Chundru wrote:
Hi Doug,
The IEC 61000-4-2 standard is a loosely defined spec. It only specifies
a few
parameters for the discharge current and with pretty big tolerances (peak
current has +/-10% tolerance, rise time has a range from 0.7 ns - 1 ns and
current at 30 ns and 60 ns have +/-30% tolerance). Consequently it is possible
for all the commercially available ESD generators to meet the specifications
but still produce vastly different discharge current pulses. For example, one
generator might produce a slowly falling first hump and another generator
might produce a rapidly falling first hump as the fall time is not specified
in the standard. This results in big differences in current derivatives (didt)
which in turn results in big differences in the fields coupled by the two ESD
generators to the EUT.
The standard does not specify the transient fields generated by the ESD
generators which are a combination of fields caused by the discharge current
at the tip of the generators and the fields caused by the faster currents
inside the ESD gun bodies. This variation in fields among ESD generators is a
bigger contributor to the un-reproducibility of test results (soft failures)
than the variations in the discharge currents (hard failures) since the
current is somewhat regulated by the spec but not the fields.
Thanks,
Ram
EMC Engineer
Apple Inc.
________________________________
From: Douglas Smith <[email protected]> <mailto:[email protected]>
To: emc-pstc <[email protected]> <mailto:[email protected]> ; Si-List
<[email protected]> <mailto:[email protected]>
Sent: Wed, December 8, 2010 9:45:25 PM
Subject: [SI-LIST] variations in ESD simulators
Hi All,
My latest monthly article is out!
Technical Tidbit - December 2010
Comparing "IEC 61000-4-2 Compliant" ESD Simulators
Abstract: IEC 61000-4-2 compliant ESD Simulators (150 pF/330 Ohm
network)
arerequired to meet a specified waveform. Results are presented here
comparing the current waveforms delivered into a metal tabletop
(Horizontal
Coupling Plane of IEC 61000-4-2) by three different simulators. The
results
were not as uniform as expected. The data presented has implications
for the
reproducibility of ESD testing.
The link to the article is: http://emcesd.com/tt2010/tt120210.htm[1]
Doug
-- -------------------------------------------------------------- ___ _
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Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _
TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 |
q-----() | o | Email: [email protected][2] \ _ / ] \ _ / Web:
http://www.dsmith.org[3]
--------------------------------------------------------------
--- Links ---
1 http://emcesd.com/tt2010/tt120210.htm
2 mailto:[email protected]
3 http://www.dsmith.org
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