[time-nuts] Data collection cycle -- multiple sources to one counter?

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Jun 19 07:56:56 UTC 2005


In message <42B4BE4F.5030802 at febo.com>, John Ackermann N8UR writes:
>I want to monitor all my atomic devices over the long term against GPS. 
>Rather than devoting one counter to each source and gathering a lot more
>data than is useful, I'm going to use a GPIB-controlled coax switch to
>route the 1pps from each source into the counter START input.  That way
>I can alternately read each source for X minutes against GPS.
>
>My question is whether there is an optimum "X" for the time to dwell on
>each source.

What you really need to look at is how often you revisit each source
so that you don't get roll-over ambiguities.

Switching too fast will also wear out your relays, and that is one thing
to be wary about buying automation multiplexers on eBay:  A lot of what
is available is there because relays started being unreliable.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.




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