[time-nuts] Comparing PPS from 2 GPS units

timenuts at triplespark.net timenuts at triplespark.net
Thu Dec 13 23:06:15 UTC 2012

On Dec 13, 2012, at 4:57 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> Suppose I want to compare the PPS outputs of 2 GPS units.  The problem is
> that I don't know which one will happen first.
> If I feed them into the start/stop inputs of a typical timer/freq box, I
> don't know which is which.  If I get them wrong, the answer will be
> 0.999999xx seconds rather than the -0.000000xx that I want.
> [...]
> Do any of the counter/timer boxes have a mode for this?  If so, is there
> a buzzword I've overlooked?
Counters like the Agilent 53230 actually WILL output negative delays 
in this case as long as the delta is still small. This is a quite useful 
feature in such cases...

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