[time-nuts] Rubidium standard

Hal Murray hmurray at megapathdsl.net
Thu Nov 12 07:15:44 UTC 2009


> I was told by a Technical Support Engineer from Symmetricom Global
> Services that "The typical life span is ~10 years for these Rubidium
> Time Bases".

> This is in response to my request for information on a Ball/Efratom
> PTB-100.

> Is this a typical life span of a rubidium standard?

It's lower than what I would expect.  The target market is the Telco and Cell 
Phone industry.  They expect (or at least used to) long lifetimes.

Maybe "life span" means how long they run it, planning to replace it with 
newer gear long before it actually wears out.

I would have expected more like 20 years of useful life.  That's running 24x7 
in a reasonable environment.  That's also with hacker reliability, aka it's 
not a disaster if it dies.  So if you get one that was dumped by a Telco 
after 10 years, it's not crazy to run it 24x7 and expect many more years.  
(Just as long as you don't go crazy if it doesn't last that long.  I can buy 
a lot of surplus stuff for the price of new gear as long as I'm willing to 
tolerate the time gaps and effort of replacing it when it dies.)


The LPRO-101 blurb says:
  Amb.Temp: 20 °C 25 °C 30 °C 40 °C 50 °C 60 °C
  MTBF (hrs) 381k 351k 320k 253k 189k 134k

A year is 8760 hours (ignoring leap years).  Call that 10K.  So they expect 
25 years at 40C and 32 years at 30C.

That's calculated MTBF.  YMMV.


> Do some standards last longer than others?

I'm sure some are better than others.  I don't have any data.


> What are the symptoms of a failing rubidium bulb? 

Externally?  It stops working.  The error signal (maybe a LED too) will go 
on, or rather the locked signal (open collector?) will go off.

The frequency stability will fall off a cliff.




-- 
These are my opinions, not necessarily my employer's.  I hate spam.






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