[time-nuts] Of rubidium life and piggy-bank anemia....
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sat Dec 1 16:29:58 EST 2007
John Ackermann N8UR wrote:
> John Ackermann N8UR said the following on 12/01/2007 04:07 PM:
>
>
>> I use the 100 second average for two reasons: first, it results in a
>> somewhat better resolution than the 2ns native of the HP-5334A TIC,
>> which may or may not be meaningful in the ADEV calculation given the PPS
>> noise. Second, it smooths the peak-to-peak noise, particularly from the
>> GPS, and makes for smoother phase plots, particularly when one of the
>> sources is GPS (I realize that 100 seconds isn't long enough to
>> integrated out the GPS noise; when I do my long-term plots, I further
>> reduce the data to tau = 1 hour and even tau = 1 day which is more
>> meaningful).
>>
>
> By the way -- another reason I linger on each PPS pair for 100 seconds
> is to slow down the wear rate on the relays in the 59503A switch!
> They're good for millions of cycles, but why switch every 1 or 10
> seconds when there isn't any measurement gain from doing so? And, if
> I'm going to sit in one place for 100 seconds, I may as well take 100
> readings instead of just 1. :-)
>
> John
>
>
John
Deadtime issues only arise if one combines successive 100 second
measurements separated by (N-1)x100 seconds.
Finite relay lifetime is an issue if one is logging for months or years
on end.
Bruce
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