[time-nuts] Cesium Beam Lifetime

Didier Juges didier at cox.net
Tue Feb 13 22:12:40 EST 2007

Can't help with Cs tubes, but the HP 5370 can do 12 digits/second and 
many other amazing things, such as 20pS resolution time interval in 
single shot, and 0.1pS in repetitive mode.

This is what I have learned about counters lately:

The 5370A is relatively common on eBay, I bought two units last year, 
for $110 and $50 respectively. Both had ROM socket problems, which I 
have not permanently resolved and which will probably require socket 
replacement, as the problems come and go. Most of the time, the counters 
work, and sometimes I have to take the cover off, pull the ROM board and 
wiggle the ROM chips). The 5370B is the same with slightly better 
firmware (faster transfer rate over the GPIB in raw mode and support of 
CIL/MATE language I believe, other than that, same performance). The 
5370B is not as common and commands higher price.

If you see a cheap 5370A with screwed up display, that's a good 
potential buy, since it will most likely be socket problems which, while 
aggravating and time consuming, should not be too expensive to fix (buy 
a dozen 24 pin machined sockets and have a quality afternoon with the 
desoldering iron)

Alternately, the 5334(A or B) is a very nice counter that does time 
interval with 2nS time interval resolution and 9 digits/sec. The 5334 
draws about 30W (and no fan) versus 200W (and a noisy fan) for the 5370, 
so if you run long term tests, the 5334 is a lot nicer to have in the 
shack. The difference between the A and B is also CIL/MATE language for 
the B model, a few more built-in features for the A model, but basic 
specs are the same. I bought mine for $40 on eBay, no HP 10811 though.

There is the HP 5316, which is smaller than the 5334, and does 7 
digits/second and 100nS time interval resolution in single shot. 
However, it seems to sell for about as much as the 5334.

The 5370 normally comes with an HP 10811 time base, the 5334 does not, 
unless you have the high stability option, which seems fairly rare on 
those instrument. The stock time base on the 5334 pretty much sucks 
(with all due respect to the designer who was constrained with 
unrealistic cost expectations).

Didier KO4BB

SAIDJACK at aol.com wrote:
> Hello guys,
> I got my FTS4050 Cesium Reference, and have it up and running. It  works 
> quite well.
> The Beam current reads 1.8V (I guess this means 1.8mA?), and Zeeman works.  I 
> am now fine-tuning with GPS.
> Some questions I had:
>   * Can I read the remaining lifetime of the Cs tube out of the  beam-current 
> somehow?
>  ....
> Lastly, I am looking for a cheap counter that can do 11 or 12 digits  
> accuracy in a 1s intervall (I think the 53132A or SR620 can do it, but they are  
> quite expensive). Any suggestions? 
> Thanks in advance!
> Said

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