In message <CALH-g5YuKCDiyGxDf4s-MhHtK=ds7qr8z2st17jrqilwvr0...@mail.gmail.com> , Jim Palfreyman writes:
>Primary Standards are ones which don't have to be calibrated against others. >My understanding is that Caesium and Hydrogen masers are Primary Standards >(in our field). > >Secondary Standards are calibrated against the Primary Standards. My >understanding is that Rubidium is an example of a Secondary Standard. Almost, but not quite. Primary standards run at an intrinsic freqyency which is determined by the atomic/physical principle used. Secondary standards run at a frequency which is different from unit to unit due to side-effects from the physical principle used. Rule of thumb: If the timekeeping atoms are not in vaccuum, it's not a primary std. >But why is it that Caesium Clocks and Hydrogen Masers have an adjustment >facility? Because there are external effects that need to be cancelled out, mainly the magnetic field from the earth. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
