Jim wrote:
If I receive WWV, and measure it appropriately, can I say that my
time, accurate to 1 second, is traceable to NIST, since they
broadcast it quite accurately, and I can bound the uncertainty
contribution from the propagation and electronics to less than a second.
That is, NIST certifies publicly that WWV is "on frequency" and "on
time" with a certain precision. Do I need to go to NIST and pay
them to give ma piece of paper that says this, or can I use their
published data?
If you are talking about legal traceability, you would need to follow
all of the requirements of legal metrology. The place where most
"little guys" fall down with respect to traceability is demonstrating
competence.
Typically, one would not get a piece of paper from NIST, although
that is one potential way. One would instead become accredited to
the relevant ISO/IEC standard through a body other than NIST (thus
certifying that your procedures are good enough to maintain
traceability), then play by all the rules to keep the chain unbroken
(most relevantly, making periodic measurements of WWV and comparing
them to the published data).
Of course, the situation you posit -- time with an uncertainty less
than 1 second -- is a very easy target, so demonstrating competence
would seem (to an engineer) not to require accreditation. However,
as you noted in a later message, someone other than yourself needs to
audit your procedures. In the real world, this is done by
accreditation. In principle, I suppose you could have anyone you
want audit your procedures, but the customers for your "accurate to 1
second" time service might want someone they have heard of doing the
auditing -- in which case, you're back to accreditation.
Best regards,
Charles
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