FreeLists / si-list / [SI-LIST] Re: [SI-LIST]EMI from two systems

[steve weir <weirsi@xxxxxxxxxx>]

Boris,

How about putting one or the other of the devices in a well sealed 
metal box with just the cable exiting?  When the main offender goes 
into the box, the emissions should drop, provided that the problem 
isn't mostly CM on the cable.  If the noise doesn't drop with one or 
the other devices in a well sealed box, then repeat but adding a CM 
ferrite over the cable.  Unless you are really cursed and also have a 
quarter-wave problem then you should get enough information to tell 
you the basics of what is going on.

Steve.
At 01:59 AM 5/16/2006, Boris Traa wrote:
>In my opinion EMC and SI are related topics. For that reason I woul like
>to posit the following problem.
>Assume two battery supplied systems A and B are connected to each other
>via just one digital interface cable (e.g. USB) and positioned 80 cm above
>a reference plane. No more cables have been attached. If the EMI-level of
>this combination is to high I would like to investigate whether it is
>system A or B.  Switching A and B off alternately is no option because it
>will lead to a malfunction of the other system.
>I could measure the CM-current through the interface cable but than I can
>not determine the main cause.
>Who can offer me a nice idea?
>
>Kind regards
>Boris Traa
>System design engineer EMC
>
>It's the currents that make circuits work or fail.
>
>Philips Applied Technologies/EM&C Competence Center
>Room 1.024
>High Tech Campus 26
>5656AE Eindhoven, The Netherlands
>Tel: ++ 31 40 27 43766
>Fax: ++ 31 40 27 42224
>E-mail:  boris.traa@xxxxxxxxxxxx Seri: nlv09273@nlwayhp
>
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