FreeLists / si-list / [SI-LIST] Re: Question on radiation limits

[Dave Barr <Dbarr@xxxxxxxxxxxxx>]

Anbazhagan,
   At a previous employment I did Class B pretesting at a 'quiet', well
calibrated 10m OATS site. The actual certifications were done at another lab
that shot entirely at 3m. Frequencies below 100 Mhz that were obvious at the
OATS did not show up at 3m due to the lack of far field development. The
certification lab actually subtracted 10db from all of the 3m measurements
and submitted a report as if the testing had been done at 10m!
   When questioned about this practice their staff replied that NIST was
allowing this procedure for some interim period until certifiers could get
their laboratories into full compliance.
   I am out of this loop presently (thankfully!) but as I recall, if you
read CISPR carefully, 3m was to be used for more making precise measurements
where ambients are involved, it was not the intention to shoot entirely at
3m.
   Also, as other readers have mentioned, cable positioning is paramount. If
you did not maximize your emissions at frequencies of concern, another
independent lab might do so to your dismay.    Regards   -Dave Barr

AAnbazhagan@xxxxxxxxxxxxxx wrote:

> Dear All,
>
>    Though it is not strictly related to signal integrity, I have a ques=
> tion
> on the radiation limits set by the CISPR (Eurpoean emission standard,
> EN55022 for emission and EN55024 for immunity).
>
> We have a got a lab in which we did the radation test in a fully anecho=
> ic
> chamber at 3 m distance (Antenna to EUT horizontal distance) to get the=
>  CE
> certification. The limit was set as 40.35 dB=B5V/m from 30MHz to 230MHz=
>  and
> 47.35 dB=B5V/m from 230 to 1GHz.
>
> The same test was conducted in another lab located at a different count=
> ry.
> There they had set the limit as 30 dB=B5V/m and 37dB=B5V/m and the boar=
> d failed
> with that limits.
>
> Which one of the limit is correct? It was argued that the 40dB=B5V/m li=
> mit
> for 3m distance is valid only for OATS and not for anechoic chambers.
>
> Can someone clarify it.
>
> Thanks
> Anbazhagan.
>
> =
>
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