[ntp:questions] PPS versus serial offset

detha detha at foad.co.za
Wed Aug 28 13:24:51 UTC 2013


On Wed, 28 Aug 2013 12:19:38 +0000, Steve Kostecke wrote:

> On 2013-08-28, David Taylor <david-taylor at blueyonder.co.uk> wrote:
> 
>> detha <detha at foad.co.za> wrote:
>>
>>> http://detha.co.za/ntp/ntpmon.20130828.jpg
>>
>> I would be more worried about the 11 ms step in the PPS at about -155
>> hours...
> 
> The PPS signal is plotted in green and does not diverge visibly from 0.
> 
> The blue line, which displays the 11ms jump, is labled "stratum 1". It is
> very likely the system offset.

It is a nearby (~15ms) server that also happens to have a GPS -
normally quite reliable but something apparently upset it for a bit. The
PPS here pretends to stay within +/- 15us

-d



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