[time-nuts] Primary Standards...

Rob Kimberley rk at timing-consultants.com
Wed Feb 24 12:38:21 UTC 2010

Yes, and no..

Time as we know it (UTC) is coordinated at the BIPM in Paris between
observations from primary standards at contributing laboratories and also
earth rotation measurements. Each lab contributing will at any time (excuse
the pun) have a small time offset with regard to UTC. E.g. time from NPL in
UK would say be offset from UTC at any time by a few microseconds, and would
be designated UTC-NPL. Worth reading

Interestingly there is a lot of research into more stable clocks using
Mercury and Ytterbium. This then leads to discussion about a future possible
re-definition of the second (which IMHO will happen).

Rob Kimberley

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Mike S
Sent: 24 February 2010 12:14 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Primary Standards...

At 07:46 PM 2/23/2010, Rick Karlquist wrote...

>The TAI is a weighted average to improve short term stability and
>to average out random frequency errors.

IOW, there is a variance from clock to clock. So, if there are 80 
different clocks, are there 80 different seconds, or 80 imperfect 
clocks? Is this a problem with the definition (i.e. Cs resonance is 
unstable), or with the clocks?

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