How would you relate the tolerance of placement of system components like
cables or PCs (in cm) to measurement uncertainty? Just setting up for the
next test can make a few dB difference. In a large system, it may even
affect antenna placement in the chamber to get the right distance to the
EUT.
Separately, in ESD testing, the poor specification of the simulator in
standards, like IEC 61000-4-2, leads to uncertainty (that one cannot
calculate) that far exceeds any uncertainty calculation one could make on
ESD testing. Until we fix the standards, uncertainty calculation for ESD
testing is meaningless. What is needed is a maximum di/dt limit everywhere
on the current waveform and a radiation spec on the simulator. And this is
only for contact discharge. For air discharge, the large uncertainty of the
discharge itself will likely dominate unless hundreds of discharges are
used at each point to reach statistical significance.
Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108
Email: d...@dsmith.org Website: http://dsmith.org
On Fri, Sep 1, 2017 at 9:05, Knighten, Jim L <jim.knigh...@teradata.com>
wrote:
A good practice is to use your calculated measurement uncertainty for
emissions as your minimum margin requirement.
That will often put you in the 3-4 dB range.
Jim
____________________
James L. Knighten, Ph.D.
Teradata
17095 Via Del Campo
San Diego, CA 92127
858-485-2537
From: Kim Boll Jensen [mailto:k...@bolls.dk]
Sent: Friday, September 01, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] God EMC practice
Hi
One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.
I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.
Does anyone have some good references on this subject?
Best regards,
Mr. Kim Boll Jensen
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