[time-nuts] Confused about Rubidium oscillators

Marek Peca marek at duch.cz
Wed Nov 14 17:04:28 UTC 2012


Hello,

> "There are no “wear-out” or “use-up” mechanisms in a Datum
> Efratom Rubidium oscillator."
> (..)
>
> But also:
>
> "Unlike a quartz crystal oscillator which has no clearly-defined "wear out"
> period and, if well-designed, can actually improve as time goes on, a Rubidium
> reference has a definite lifetime associated with its lamp:
> (..)
>
> so maybe both points of view are correct?
> (..)

Yes, both of the points bear some meaning. The Rb does not age 
substantially by means of long-term frequency variation, unlike typical 
quartz.

However, the Rb lamp is maintained hot (~100Celsius in LPRO-101) and 
contains aggresive light metal, therefore one day the glass will "wear 
out" and the lamp does not shine enough or shine at all. The Rb synthesis 
circuit will be able to detect such a situation and you are at least 
informed, that thigs went wrong.

Of course, there are other minor circuit elements inside of the Rb clock, 
which may vary in long term -- eg. magnetic field bias regulator, output 
buffer. But these do not age systematically with predictable sign and 
magnitude.


Regards,
Marek


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