Actually even crystal oscillators start to lose time in hours... A rubidium can holdover for days and a cesium can holdover for more days... None are perfect. Cesium 133 resonates between different energy states 9,192,631,770 times each second with almost no variation. So a clock that ticks to that resonant frequency will be highly accurate. The National Institute of Technology's most accurate cesium clock, which along with a similar device in Paris is the most accurate in the world, will neither gain nor lose a second in 20 million years. I was sorta joking really. It's kinda like the cesium wrist watch you seen that one gregbert?
http://leapsecond.com/pages/atomic-bill/ Bill On Mon, Jan 13, 2020, 3:48 PM gregebert <gregeb...@hotmail.com> wrote: > It's really a matter of what you want for a reference. A > Rubidium/Cesium/whatever reference will give you a very stable 10Mhz timing > reference, but it *wont* give you the official time-of-day. Every so often, > there are corrections to official world time and if you're using a stable > timing reference you still have to code those changes into your clock. > > When you use GPS or NTP, all of that global time update stuff is handled > for you, but between updates your time will drift slightly though that > amount of drift is probably milliseconds or less. It would be cool/amusing > to monitor the drift in realtime versus a local atomic reference. I believe > NTP monitors drift and attempts to correct for it and if drift is small > enough it will periodically skip updates; my RasPi is logging about 20 NTP > updates overnight. > > I recall some of the temp-controlled quartz-crystal ovens were holding +/- > 0.1PPM , which is roughly 1 second per 100 days. Whereas an atomic source > is on the order of 1 second per 30+ *years* . > > -- > You received this message because you are subscribed to a topic in the > Google Groups "neonixie-l" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/neonixie-l/o31sfIZ1PiA/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/ad4b61cc-70e7-44b8-917b-0999688e4a60%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/ad4b61cc-70e7-44b8-917b-0999688e4a60%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CADToqn09_67uzeoodPnxHh4wL-3KR1DUo-TjM_NShMmtJj6cqQ%40mail.gmail.com.
