[time-nuts] CS reservoir depletion
paulswedb at gmail.com
Thu Jan 13 20:00:44 UTC 2011
Hi Tom been quite a while hope you are well.
The never run out comments, not from me. Look at the previous thread I
tagged onto. My humor is that most of the CS tubes we get are very long in
the tooth usually way past whatever anyone would say they are good for.
However my 5065 Rb is still going strong, knock on wood after 2 X what was
stated for life.
Unfortunately my 5061 was actually dead on arrival. But you take your risk
at $125, right?
Didn't really matter that it did not work as much as I might have liked it
to. I learned a heck of a lot from trying to get it to. Also from support on
this list. If it had worked I would not have really learned a thing.
Maybe I will find a tube one day. But pretty sure I won't be drilling a hole
and pouring some CS into it.
Oddly enough I picked up a HP super-duper pico amp meter and source and when
the dust settles on several projects will hook it up just for the heck of it
to see if there is even a drop of I beam current hiding behind some magnets
in the tube.
On Thu, Jan 13, 2011 at 2:30 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
> Really interesting thread. About a year ago on this thread the same
>> discussion occurred.
>> Several thoughts along these lines and frankly I know little accept for
>> I read here and online.
>> I would agree the CS never runs out. Accept for one minor point. We tend
> get these things way beyond HPs end dates by many years. So is it really
>> This threads a bit different then the last one. The last one described
>> opening the internals and various effects from trying to refill the
>> This would be the first insight that I have in the fact that the systems
>> polluted perhaps.
> What I've heard is that the lifetime of the 5071A high-performance
> tube is around 7 years (when the cesium runs out) and the lifetime
> of the standard tube is up to 20 years (when the EM fails). There
> are other failure modes too so YMMV. Not sure about 5061A and
> other tubes. There are variations within the 5071A tube as well
> (including the short-lived turbo tube), so take this only as a rough
> estimate (but do see the chart in paper10.pdf below).
> As you may know the high-perf tubes have higher performance
> simply because they use a much higher flux of atoms (beam
> clock noise is a simple function of flux) and so they run out of
> "gas" proportionally faster. Like a candle burning twice as bright,
> or for you Neil fans, it's better to burn out than to fade away.
> But there's lots of data on this subject since most of the national
> timing laboratories use 5071A in quantity and they collect all
> the internal performance data that the 5071A makes available
> over the RS232 port. Some papers on the subject include:
> End-of-life Indicators for NIMA's High-performance
> Cesium Frequency Standards
> Maintenance of HP 5071A Primary Frequency Standards
> at USNO
> An Automated Alarm Program for HP5071A Frequency
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
More information about the time-nuts