Every measurement uncertainty seminar I've ever been to, since the mid
80s, has concentrated on it as a measure of the labs ability to control
uncertainty. In every case, from NIST to NPL, they have been adamant
that uncertainty has _nothing_ to do with the pass/fail criteria. The
ironic thing is that labs would argue that, by being more rigorous an
finding higher uncertainty, they would scare away customers who found
less rigorous lab's smaller numbers attractive.
Obvious puns about uncertainty resisted,
Brent DeWitt, Lab Manager iRobot
Milford, MA
On 7/12/2023 11:02 AM, Patrick wrote:
what year did measurement uncertainty become a required component of
lab accreditation?
was there massive radio interference at homes and in offices that
suddenly ceased the year after?
asking for a friend.
On Tue, Jul 11, 2023, 10:28 Chas Grasso <charles.gra...@dish.com> wrote:
When the concept of measurement uncertainty came about, the
company I worked for at the time decided that
irrespective of the technical niceties of statistics if emission
exceeded the spec but was within the stated MU,
then that was still considered a FAIL. The difficulty came when
the emission PASSED but was within the MU.
The company decided that - even if the testhouse would not declare
the pass, the product still shipped.
In other words - life as usual.
On Tue, Jul 11, 2023 at 9:13 AM Ken Javor
<ken.ja...@emccompliance.com> wrote:
*
This message originated outside of DISH and was sent by:
ken.ja...@emccompliance.com
*
------------------------------------------------------------------------
Not in the commercial sector, but people try this argument all
the time when failing a MIL-STD-461 limit by less than 3 dB,
on account of the measurement system integrity check has to be
within that margin.
They /never/ express such concerns when they pass within 3 dB
of the limit, however.
--
Ken Javor
(256) 650-5261
*From: *Brian Kunde <bkundew...@gmail.com>
*Reply-To: *Brian Kunde <bkundew...@gmail.com>
*Date: *Tuesday, July 11, 2023 at 9:31 AM
*To: *<EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject: *Re: [PSES] FCC Part B questions
If I may pile on late, keep in mind that measurement
uncertainty is Plus or Minus (±). Years ago when I was with a
previous company, we had a buy/sell piece of junk product that
we were selling with our company's brand/name on it. It was
audited in Sweden as part of their surveillance program and it
failed by 2dB. The test lab said they could not say it FAILED
because 2dB was within their measurement uncertainty, so we
could continue to ship and sell this product in Sweden.
Has anyone else ever experienced this?
Thanks,
The Other Brian
On Sat, Jul 8, 2023 at 8:28 AM Brent DeWitt
<bdew...@ix.netcom.com> wrote:
Hi Brian. It's not entirely clear which measurement range
you are asking about, but I'll assume conducted emissions
in the range of 150 kHz to 30 MHz.
Short answer: You can skip QP and Avg detection if the
peak detection level is below the Avg detection limit.
No margin is "required" to pass any emissions limit. Zero
dB margin is still passing. That said, measurement
uncertainty in that range is generally 3-4 dB, so having a
passing margin greater than that gives you some confidence
that a re-test at another time and lab will still pass.
Hope that helps.
respectfully,
Brent DeWitt
Milford, MA
On 7/8/2023 12:38 AM, Brian Gregory wrote:
Hi there,
A question came up that I can't answer w/o a copy of
Part 47.
Does the FCC report require Quasi-Peak (QP) data, or
just Avg and Peak. When do peak readings trigger the
need to report QP? I'm pretty sure Part 15 has AVG
and QP limits listed.
Next was what sort of margin is expected in order to
pass CE emissions requirements (CISPR 16 or 32)?
Memory serves that one wants 3dB of margin, but
memories can be imperfect!
"Colorado" Brian
720-450-4933
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--
Charles Grasso
Dish Technologies
(c) 303-204-2974
(w) 303-706-5467
(h) 303-317-5530
(e ) charles.gra...@dish.com
(e2) chasgra...@gmail.com
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