[time-nuts] Sensitivity to g in atomic clocks

Tom Van Baak tvb at LeapSecond.com
Tue Jan 11 18:37:57 UTC 2011

> While sensitivity to g is an usually specified parameter for crystal
> oscillators, I've been unable to find any indications for atomic clocks, say
> 5071A, or more modestly LPRO. Can anybody point me to any source of info on the
> subject?
> Thanks,
> Antonio I8IOV

Hi Antonio,

You may find some information on g-sensitivity of rubidium
in old FCS or PTTI papers. There are high-rel rubidium for
the military and space applications, so practical issues of
acceleration and jerk sensitivity have been well researched.

The other thing you could do is quickly and/or very slowly
turn over a running LPRO and report what happens. Like
what we do with quartz, try it on all three axis. It would be
a fun experiment.

For a 5071A the frequency shift is gh/c². Earth tides cause
a couple of ten cm change during the day; this change in
local g affects the output by parts in 10^17; way too low to
be detected with a 5071A but getting near to the capabilities
of ion clocks. See:

For some info on g, tides, and clocks see:

To detect changes in g with a 5071A you can raise the clock
by many meters. For example, g is about 9.808 m/s² at sea
level in Seattle but 1 km up it's closer to 9.805 m/s². A 5071A
runs about 1e-13 faster at 1 km elevation compared to one
at sea level. This is large enough to be measurable. See:


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