[time-nuts] Reliability of atomic clocks

Bob Camp kb8tq at n1k.org
Sun Mar 27 10:13:32 EDT 2016


Hi

The “typical life” numbers on the tubes in the various Cesium standards
are fairly accurate. Most units that are well cared for “die” when the tube
goes out and come back to life when it’s replaced. The tube life dominates
the MTBF in this case. 

Rb’s are a device that by it’s (possibly unfortunate) physics needs to run 
hot. The vast majority in service are “miniature” in comparison to a 5071 or
a 5065. That drives the temperatures of all the parts up. MTBF on them
is very “temperature of use” dependent. They fail for a range of reasons
as the parts in them die of “hot old age”. 

Efratom had some pretty good data on MTBF vs temperature in the LPRO 
data sheets. The internals of all the designs are similar enough that it likely 
applies over more than  just one design. Temex has a similar data snapshot. 
I have a sample of the Temex units in front of me as I type this. They died 
as one would expect - from something other than the bulb. Capacitors, IC’s, 
crystal drift, board corrosion, being crusted (physical damage), each pop up
in the sample. 

Bob

> On Mar 27, 2016, at 7:53 AM, Attila Kinali <attila at kinali.ch> wrote:
> 
> Moin,
> 
> Maybe someone here can help me.
> I am looking for data on the reliability of atomic clocks.
> I.e. how often and, if possible, how they fail.
> 
> Unfortunately, if I google for reliability then all that pops up
> are descriptions of the accuracy and stability of atomic clocks.
> If I go for MTBF I only get two papers from the 70s that tackle
> the problem in general, without giving any data.
> 
> Does someone know where I could find current data about MTBF and
> failure modes of atomic clocks? Given the number of 5071's installed
> in labs, there must be at least some data on them....
> 
> 
> 			Attila Kinali
> 
> -- 
> Reading can seriously damage your ignorance.
> 		-- unknown
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