[time-nuts] Question for the cesium nuts.

SAIDJACK at aol.com SAIDJACK at aol.com
Fri Mar 16 22:59:25 EDT 2007


 
In a message dated 3/16/2007 18:32:58 Pacific Daylight Time,  
martelno at yahoo.com writes:

Also,  some high end rubidium (such as Perkin-Elmer)
manufacturers are able to  develope 133Rb clocks having
> 450 000 hours MTBF! That'a a lot of  nanoseconds!



Hi Jack,
 
we cannot expect the units to work that long. Hard Disks have >50K MTBF,  and 
fail all the time in much less time depending on how they are used  etc.
 
MTBF is a mean, meaning in the real world the Perkin Elmer unit  could fail 
in the first 10 minutes, just that the statistics for that to  happen have 
pretty low probability.
 
When they calculate MTBF, they probably don't take into account external  
effects such as AC voltage spikes due to janitors pluggin-in vacuum's or due to  
lightning etc, earthquakes, user obuse, water damage, movement, effects of UV  
light on plastik parts such as cables, Tin Whisker shorts, electrolytic  
capacitor dryout, mouse damage, etc. I think it's pretty useless to say a  piece 
of equipment has a MTBF of over 50 years. Then again that's only an  opinion...
 
bye,
Said



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