I agree with your interpretation of the enquiry. I think it is necessary
to watch out for the legs. if they are frames (or some more complex
construction) rather than single pillars, becoming resonant loops at
some frequencies. I suppose single pillars could also resonate.
On 2023-12-28 22:00, Ken Javor wrote:
Ken et al,
I think the query was just the opposite. The tabletop is wooden, but
do the legs need to be wooden as wel? The FCC paradigm (AFAIK)
places the test sample 80 cm above ground, thus /limiting/ parasitic
capacity. My gut response is they should be fine with metal legs, as
long as the tabletop is thick enough to limit stray capacity. If one
had OCD tendencies, one could measure the capacity between a piece of
metal laid on the tabletop and the ground plane, and as long as the
capacity were suitably low (single-digit picofarads?) that would suffice.
--
Ken Javor
(256) 650-5261
*From: *Ken Wyatt <[email protected]>
*Reply-To: *Ken Wyatt <[email protected]>
*Date: *Thursday, December 28, 2023 at 3:53 PM
*To: *<[email protected]>
*Subject: *Re: [PSES] Metallic table for conducted emissions?
Hi Brian,
The answer is yes and no. Yes, you can get a general idea, but no, you
really need a ground plane to conduct the CM currents back to the
LISN, which needs to be bonded to the plane. Just find a metal supply
store and buy enough aluminum to cover one of your benches. In a
pinch, and for quick troubleshooting, I just tape down heavy duty
aluminum foil and copper tape the LISN to the foil.
You’ll see examples of the technique in my Volume 2, Chapter 3 of the
trilogy.
Cheers, Ken
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On Dec 28, 2023, at 2:13 PM, Brian Gregory
<[email protected]> wrote:
Hello fellow experts,
we're looking to build a conducted emission pre-compliance test
station to FCC Part 15 Subpart B requirements (residential
applications).
Is a non-metallic table a necessity for reasonable accuracy?
We have a number of lab benches with wood tops and metal legs that
would fit far better than jamming an all wooden, non-folding table
into our modest space.
thanks all and Happy New Year,
Colorado Brian
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