Agreed, as is the easiest solution - physical separation between EUT
and the traffic generator. All peripherals that are driven by the EUT are
located within short physical distance as prescribed by the various standards,
but Ethernet devices CAN BE, meters and kilometers apart so I take the position
that the traffic generator can be physically separated from EUT as well.
Besides, I can't see the data flow and errors in real time if the analyzer were
in the chamber with EUT. Real peripherals running next to the EUT, test
generators removed.
In at least one instance I could monitor my traffic quite nicely as
long as I didn't try to move the mouse that was connected to the analyzer
because it was locked up. Plugged the opening into the immunity chamber and
problem went away. It is still a much better way to generate and monitor the
traffic and errors it just takes a little bit of caution.
Gary
I think that if you ever tried to run an RF immunity or radiated emissions test
on these analyzers it would perform horribly.
-----Original Message-----
From: Douglas C. Smith [mailto:d...@emcesd.com]
Sent: Friday, April 19, 2002 2:18 PM
To: Gary McInturff
Cc: Pommerenke, David; Chris Maxwell; emc-p...@majordomo.ieee.org
Subject: Re: Suitable CDN for IEC61000-4-6 ethernet 10/100
Hi All,
Just a word of caution about test equipment used to measure EUT
performance, such as a LAN-analyzer or similar equipment that counts
errors. My experience has been that some of this equipment is itself
very susceptible to EMI. In a recent case, I had to move a bit-error
tester to the other side of the lab on the end of a fiber in order for
it not to register errors while testing the EUT. It was so sensitive
that low levels of ESD in the room (not applied to the EUT), that did
not affect the EUT itself, caused the test equipment to register many
false positive error counts.
On a similar point, on that same job, I found the lab scope (a modern 5
GSa/sec unit) was itself susceptible. One of my techniques to measure
EMI induced noise on a board would not work because the scope displayed
more noise with a closed 50 Ohm termination, instead of my measurement
apparatus, on its input BNC than the noise I was trying to measure in
the first place.
Doug
Gary McInturff wrote:
>
> Yup, when we do immunity testing - we see the occassional crc error
> or the ilk, but I've never seen a problem with the link. We use an Ixia box
> to cram data down the lines. There are probably many other traffic generators
> that will work just fine but none of them are pocket change.
> Gary
>
> -----Original Message-----
> From: Pommerenke, David [mailto:davi...@ece.umr.edu]
> Sent: Friday, April 19, 2002 8:28 AM
> To: Chris Maxwell; emc-p...@majordomo.ieee.org
> Subject: RE: Suitable CDN for IEC61000-4-6 ethernet 10/100
>
> What you should take into account is the failure criteria for 61000-4-6 as
> seen by the EU: No degradation beyond manufactueres specification.
>
> Depending on the EUT just a few additional bit-errors at any of the tested
> frequencies may be a fail. It may not be sufficient to just look at loss of
> link. In many cases, a low level LAN-analyzer is needed to do this test.
> Otherwise, effects of lessere severeness than loosing link will not be
> detected, although they may be a fail of the test.
>
> David Pommerenke
>
> -----Original Message-----
> From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
> Sent: Friday, April 19, 2002 7:53 AM
> To: emc-p...@majordomo.ieee.org
> Subject: RE: Suitable CDN for IEC61000-4-6 ethernet 10/100
>
> >From David Sterner's message:
> "Most people use the EM clamp. We test to EN50130-4 alarm
> system limits:
> 10V, pulsed and AM modulated. The test is trivial because of
> the inherent
> immunity of Ethernet; be sure you understand the EUT and AE
> port
> partitioning algorithms."
>
> What! The test is trivial because of the inherent immunity of Ethernet.
>
> The last product that I took through the lab couldn't even take
> 3V...heck, the Ethernet cable couldn't even take 3V being put on some of
> the other cables in the chassis.
>
> Now, before everybody sends me design tips for Ethernet immunity...save
> your breath... the chassis was a purchased computer. It was EMC tested
> (with only a dummy ethernet cable and no traffic, mind you). And I have
> no design control of the ethernet circuit. We ended up using shielded
> Ethernet cables and invoking the "3meter rule".
>
> The point that I'm trying to make is...I'm glad that this test is
> trivial for your products. Obviously, you have a good design
> there....(Where were you when we were looking for a compliant mainframe
> to use with our system?) But this type of immunity performance cannot
> be attributed to all Ethernet ports in general or to the Ethernet
> protocol in general.
>
> Best regards,
>
> Chris Maxwell | Design Engineer - Optical Division
> email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797
> 8024
>
> NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
> web www.nettest.com | tel +1 315 797 4449 |
>
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