[time-nuts] Re: Primary frequency standard

[Greg Burnett]

As a side-note: After the intro of ISO 17025, our HP / Agilent 
customers’ auditors began requiring us to verify / compare primary 
standard performance against another standard, to a stated MU 
(Measurement Uncertainty). Prior to this, our “calibration certificates” 
simply stated that the primary standard met specifications by design. In 
my HP / Agilent metrology work, Boeing was our first big customer to 
require the additional verification steps for primary frequency 
standards. (These additional steps were at odds with those of us who 
understood the "by design" justification, but never-the-less were 
generally required by auditors under ISO 17025.)

At first they just required a few additional instrument “check” 
procedures (which I wrote) because their auditors had caught a 5061A 
claimed to meet “specs by design” yet not noticed to be unlocked because 
its Alarm and/or Continuous Operation lamps were out. I added some 
regularly scheduled end-user-performed meter and lamp checks (partly 
borrowed from Section III in the manual), which satisfied them at the time.

...Later came the verification against external standards, with stated 
MU, under ISO 17025

-------- Original Message --------
From: [mailto:cdelect at juno.com]
Sent: Friday, March 26, 2021, 3:42 PM
To: time-nuts at lists.febo.com
Subject: [time-nuts] Primary frequency standard

In reference to:

"It would be cool to say one has a "primary standard", .... So, I think
we should be careful with the term, it's get thrown around too lightly."

Any of the hobby grade used Cesium standards is actually a Primary
frequency standard as it does meet the definition of:

A frequency source that meets national standards for accuracy and
operates without the need for calibration against an external standard.

They ARE able to meet their accuracy specs without calibration against an
external standard.

The definition does not exclude them.

I realize that Metrology usage may be different but the definition makes
no judgement as to how performance levels!

Cheers,

Corby
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