On Fri, 24 May 2013 17:24:35 +0100,
John Woodgate <j...@jmwa.demon.co.uk> wrote:
> It's known that this clause is inadequate and it will be reviewed, but
> probably not very swiftly. It has been pointed out that the
> capacitance between the EUT and the ground plane depends on the
> permittivity of the support, which is not controlled.
Thanks both for the responses.
Actually, I didn't mind of permittivity of the insulating material
so much, which is plastic or rubber wheel of the casters/rollers in
this case.
However, I mind of the possible ambiguities, such as:
o If non conductive roller/casters part of the EUT can be used as
the insulating support, how about commonplace casters like this?
http://commons.wikimedia.org/wiki/File:Absolex_san.jpg
If such casters can still be used as the insulating support,
how about machine rollers like these ones,
http://www.machineroller.com/
which are mostly metal but surface of the wheels are covered by
plastic or rubber?
o If such casters/rollers can be used as the insulating support,
which position of the rollers/casters should positioned at the
specified height of about 0.1m?
Top of the caster/roller, or bottom of its metal component?
o This standard didn't use the term "may" about this.
However, if it is an option, it would be expected that one
laboratory may put an EUT on the GRP without 0.1m support, and
other laboratory may put the same EUT on 0.1m support.
This will alter the distance between EUT's bottom surface and
GRP, and can cause additional inconsistency of the test results
between laboratories, I thought.
At this time, we would need to put such EUTs on 0.1m insulating support
for some other 61000-4-* standards anyway, and I think it would far
easier to put such EUTs on 0.1m insulating support as far as possible
also for 61000-4-4 testing.
Regards,
Tom
--
Tomonori Sato <vef00...@nifty.ne.jp>
URL: http://homepage3.nifty.com/tsato/
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