Hi There was a point in time where HP made a *lot* of the Cs standards out there.
Bob On Aug 26, 2013, at 5:52 PM, Magnus Danielson <[email protected]> wrote: > Hi, > > On 08/26/2013 01:56 PM, Bob Camp wrote: >> Hi >> >> >> On Aug 26, 2013, at 2:01 AM, Magnus Danielson <[email protected]> >> wrote: >> >>> Exactly. As you have three devices, measuring them pair-wise you get >>> three measures and three un-knowns, and you can untangle the >>> stability of each individual. If you have yet more, you can get some >>> confidence levels also as it becomes overdetermined. >> The only real gotcha is common mode drift. If all your gizmos are made same >> place / same time / same parts then they may drift the same way. In this >> case "drift" could correlate to environment rather than just to time >> (aging). Back when HP pretty much made all the Cs standards this was a >> common thing to worry about when setting up an ensemble of them. > Indeed. An independent source make sense, like a different atomic > reference mechanism, or as you propose, a different location. >> Of course you could always move your ensemble to an un-inhabited cave and ….. >> >> No, HP did not make the long tube Cs standards at NIST (as the NIST guys >> always love to point out) and they are very different animals than the ones >> you can buy. So, the international definition of the second has always been >> safe from manufacturer induced common mode. > Also, it wasn't as manufacture dominant as it has been. Not all the > commercial cesiums being used have been HP, even if HP have made a big > number of their dominance. > > Cheers, > Magnus > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
