MU seems like a decent idea but is at best just an added cost for labs. It
seems like magical thinking - as long as this number is 'good' your results are
good. I've been working in labs 20 years. The biggest sources of error are
completely ignored by MU - operator errors and poor methods to verify setup
(e.g. using a comb gen before testing). MU is being pushed into everything,
with zero added value. What value is created by having MU for verifying a
cable? If your sig gen and analyzer or VNA are crap the results of actual
testing will be as well. Having a +/- dB on the cable measurement doesn't give
you any actionable information.
We are required to have MU calculations for all these different measurements,
but the results are completely ignored. My cable cal MU could be 100 dB, but
since there are no limits or requirement to report this anywhere other than the
cable cal 'cert' it is useless data.
Right now immunity test standards only have MU as informative annexes. I fear
that the IEC or ABs will start requiring it. A huge time sink to come up with a
number that gives little information and is ignored nearly universally.
-D
On Wednesday, July 12, 2023 at 10:15:38 AM CDT, Chas Grasso
<[email protected]> wrote:
Hello Patrick, Deferring to others that have the history, as far as I can
remember
the impetus was good engineering practice.
On Wed, Jul 12, 2023 at 9:03 AM Patrick <[email protected]> wrote:
This message originated outside of DISH and was sent by: [email protected]
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 <[email protected]> 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 <[email protected]> wrote:
This message originated outside of DISH and was sent by:
[email protected]
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, howeve
-
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