Re: [SI-LIST] : Shielding Effectiveness - or when a dB is not a dB

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From: brent.dewitt@us.datex-ohmeda.com
Date: Tue Aug 01 2000 - 08:40:24 PDT


Hi Doug,

Yes, I have tried a similar approach based on an article a few years back that
used two HP 11940 probes mounted on a wooden jig. Maybe someone else on the
list can remember who the author was. It worked quite well.

Best regards,

Brent DeWitt

"Douglas C. Smith" <doug@dsmith.org> on 07/31/2000 09:53:52 PM

Please respond to "Douglas C. Smith" <doug@dsmith.org>

To: emc-pstc <emc-pstc@majordomo.ieee.org>, SI-LIST
      <si-list@silab.eng.sun.com>
cc: (bcc: Brent Dewitt/US/D-O)

Subject: [SI-LIST] : Shielding Effectiveness - or when a dB is not a dB

Hi All,

Shielding effectiveness is normally measured using plane
waves (relatively far from the source). This method of
measurement for shielding effectivenes does not always
correspond to the way a shielding material is used. It is
especially true when shielding material is incorporated
into small products, such as the new wave of wireless
devices on the market. If you rely on shielding to keep
different parts of a product from interfering with each
other, correlation of specification to use is especially
important.

The August 2000 Technical Tidbit on http://www.dsmith.org
(or http://emcesd.com) describes a simple method of
shielding effectiveness measurement that can be easily done
in the development laboratory. This measurement method can
give a better measure of shielding effectiveness that
industry standard measurement techniques when the shield is
close to the source being shielded.

Has anyone here who is into shielding used something like
this method which uses magnetic field loops?

Doug

--
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 \ _ /    ]    \ _ /         Website: http://www.dsmith.org
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