John,
Your point is well taken with regard to testing a unit while closely
matching the testing environment to the environment it will be used in.
However, we don't sell a lot of equipment to people who have 40 meters of
ground plane, either.
It is my understanding a reasonable "false" environment is an attempt to
control the testing environment and obtain repeatable results. Controlling
the table material so it does not appreciably affect the outcome of the test
seems to be consistent with that goal.
- Robert -
Robert A. Macy, PE [email protected]
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-----Original Message-----
From: John Woodgate <[email protected]>
To: [email protected] <[email protected]>
List-Post: [email protected]
Date: Friday, November 02, 2001 2:30 AM
Subject: Re: EMC test table construction plans
>
>I read in !emc-pstc that Pommerenke, David <[email protected]> wrote
>(in <[email protected]>)
>about 'EMC test table construction plans', on Thu, 1 Nov 2001:
>>For emissions and immunity you should not use any wood in the table. It
will
>>significantly (+/-2 dB up to 1 GHz for emissions , more above, +/-10 dB
for
>>immunity up to 1 GHz) change the test result. My experience has shown that
>>Styrofoam is basicly the best material.
>
>You mean that it gives the worst-case results?
>
>>There are a couple of published
>>papers on this issue. As surface material the following worked out fine:
>>
>> - Foamed PVC (rather stiff, low dielectric constant due to the foamed
>>nature), maybe 4 mm thick.
>>
>> - PE sheet, maybe 2 mm thick.
>
>Should the test conditions not reflect the actual environment in use of
>the product, rather than employ these unusual materials?
>--
>Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
>
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