Ahh Ken,
Come on now, its not broken, only a flesh wound ;-)
We do have a problem with folks piddling around in none value added detail,
which is why I'm being so belligerent about this.
Just for good measure, we disagree over Denis being correct too :-)
Cheers,
Derek.
On 10/11/2011 1:29 PM, Ken Javor wrote:
Within his frame of reference, Ward is correct, which is why this entire
accreditation process is flawed and broken. We got along without it before,
and it is adding nothing but extra costs and bureaucracy, and negative value
to the process of controlling EMI.
Ken Javor
Phone: (256) 650-5261
________________________________
From: Dennis Ward <[email protected]> <mailto:[email protected]>
Reply-To: <[email protected]> <mailto:[email protected]>
Date: Tue, 11 Oct 2011 11:15:00 -0700
To: 'Derek Walton' <[email protected]> <mailto:[email protected]>
Cc: 'Grace Lin' <[email protected]> <mailto:[email protected]> ,
'WNya'
<[email protected]> <mailto:[email protected]> , 'EMC-PSTC'
<[email protected]> <mailto:[email protected]>
Subject: RE: Table Size in Emissions test
HI Derek
The point of anything ‘nominal’ is that it starts with what is expected
and allows reasonable variations of sorts. And you hit the right words
“relating to a designated or theoretical size”. If you say you must
follow the standard, then follow it. The designated size of a table is 1m x
1.5m x 0.8m. This then is the size generally expected. It is not a
micrometer reading with 0.01m measurement uncertainty tolerances; it is a
general designated and expected size – a nominal size.
Now, and without going into uncertainties and its minutia, a 0.8m x 1.2m
table, while not typically or generally expected, could be stretched to be
within a range of what could be considered within the nominal range. Likewise
a table 1.2m x 1.8m would or should still be considered within an expected or
nominal value. To the contrary, a table 0.2m x 0.2m, for many reasons, would
not be generally considered expected and thus not nominal, but abnormal in
size for the intent and purposes of the standard.
Remembering that there are three dimensions given (i.e. 1mx1.5mx0.8m),
if we
take your ‘exception’, then I could place a device on the ground plane as
long as it was on a nonconducting surface. Yet I know of no lab nor auditor
that would accept this as a ‘nominal’ height condition for any of the
standards mentioned. I would not be able to reject or challenge their claim
that my table height was not 80cm by saying, nominal is “of, being, or
relating to a designated or theoretical size that may vary from the actual,
and I don’t have to have a table 80cm high.”
One might say, yes, but height matters. And they would be correct,
however,
the dimensions are together in the same frame of reference in the same
sentence. So any exceptions to the dimensions would have to follow the same
process. The issue then is not uncertainty and its issues, but what is
generally expected and accepted as a reasonable table for the intent of the
standard.
Remembering that standards are produced as much to make something
consistent
wherever used, then the nominal would be that which is generally consistent
within the population that uses the standard.
As to ‘bigger fish to fry’, this would be a good size fish for a lab
that
was seeking accreditation. Yes there are allowable variations, equipment
considerations, etc that can be discussed with the accrediting organization.
To say that because ‘nominal’ is used and because ‘shall’ is not, I
can do what I want, is simply not the case if they want to become accredited.
It is fairly easy and cheap to construct a nominal table of dimensions in the
standards. There is probably more money, time and effort in trying to
challenge or reject the assessment than to simply hire a carpenter and build
one.
But the choice is the labs and how they wish to relate to their
accreditation
body.
Dennis Ward
Director of Engineering
American Certification Body
Certification Resource for the Wireless Industry http://www.acbcert.com
703-847-4700 fax 703-847-6888
direct - 703-880-4841
From: Derek Walton [mailto:[email protected]]
Sent: Tuesday, October 11, 2011 10:09 AM
To: Dennis Ward
Cc: 'Grace Lin'; 'WNya'; 'EMC-PSTC'
Subject: Re: Table Size in Emissions test
Sorry Dennis,
you are not correct. Nominal means:
b : of, being, or relating to a designated or theoretical size that may
vary
>from the actual.
This is from Websters.
As you indicate, there is NOTHING that says it has to be 1 by 1.5m
I'm sorry to be so anal about this, but it is happening too much where
assessors are assessing to opinions and personal agendas. We must follow the
standard. Usually there are MUCH bigger fish to fry than quibbling over
something like this
I repeat, again, that there is NOTHING that says the table SHALL be 1 by
1.5m. Only then could a deficiency be written.
Sincerely,
Derek.
On 10/11/2011 11:43 AM, Dennis Ward wrote:
Both ANSI C63.10 and ANSI C63.4, the typical standards for which
ISO17025
accreditation is used, contain the following statement, “Tabletop devices
shall be placed on a nonconducting platform, of nominal size 1 m by 1.5 m,
raised 80 cm above the reference ground plane.
While a bit more open to variation due to size of equipment, CISPR 22
has the
statement “Equipment intended for tabletop use shall be placed on a
non-conductive table. The size of the table will nominally be 1,5 m ◊ 1,0 m
but may ultimately be dependent on the horizontal dimensions of EUT.
So while you may challenge the accreditation organization, they are
correct,
your table does not meet the ‘nominal’ size requirements for at least the
two standards ANSI C63.4 and C6310.
Other standards may also have the nominal size issue as well.
Thanks
Dennis Ward
Director of Engineering
American Certification Body
Certification Resource for the Wireless Industry http://www.acbcert.com
703-847-4700 fax 703-847-6888
direct - 703-880-4841
From: [email protected] [mailto:[email protected]] On Behalf Of Grace
Lin
Sent: Tuesday, October 11, 2011 4:16 AM
To: WNya
Cc: EMC-PSTC
Subject: Re: Table Size in Emissions test
Wendy,
When I look for an accredited ANSI C63.4 laboratory, I expect the
laboratory
has the facility as stated in the standard, including a standard size of the
table as defined in the standard. For this reason, unless the accreditation
certificate bears a restriction note, I support the auditor's comment.
>From the other point of view, many manufacturers' laboratories are for
internal use only, including my employer's. For this reason, the auditor may
be willing to accept the smaller size of the table. The question is how to
determine if the laboratory is for internal use only (for testing certain type
of products). An example is Alcatel-Lucent's EMC laboratory in New Jersey,
USA. It opens to the general public.
With regards,
Grace
On Mon, Oct 10, 2011 at 7:54 PM, WNya <[email protected]>
<mailto:[email protected]> wrote:
Dear Experts,
Recently my company went through the first ISO17025 audit. We have a
table
smaller than the standard requirement of 1.5m x 1m since our products are
small, typically 10cm x 10cm x 10cm. The height of our table was 0.8m. The
auditor wanted us to change the table size to follow the standard.
What does it matter since we never use the extra space on the table? I
do
agree we must keep to the height requirement since the floor is a ground plane
and thus it sets a fixed capacitance to the EUT and also controls the lengths
of any attached cables.
Can we reject or challenge the auditor's request? Has anyone experience
the
same situation?
Sent from Wendy.Nya iPhone
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