[time-nuts] live 50 Hz measurements

[Joe Gwinn]

 From digest vol 84 issue 7:
>Date: Fri, 1 Jul 2011 13:06:31 -0700
>From: Chris Albertson <albertson.chris at gmail.com>
>To: xformer at citynet.net, Discussion of precise time and frequency
>	measurement	<time-nuts at febo.com>
>Subject: Re: [time-nuts] live 50 Hz measurements
>Message-ID: <BANLkTindMF0T_Fu3AQuPcKhrK7uxFQsOiA at mail.gmail.com>
>Content-Type: text/plain; charset=ISO-8859-1
>
>On Fri, Jul 1, 2011 at 12:46 PM, Will Matney <xformer at citynet.net> wrote:
>  >
>>   For accuracy sake, I'd still compare the line freq. to a 
>>standard, but that's just me.
>
>If the computer used for this is also running "ntpd" the computer's
>clock is disciplined.  How well depends on what ntpd is using as a
>reference clock.

Actually, there *are* cases where ntpd is running without complaint 
but the local clock is not being disciplined.

The situation I most often run into is that ntpd has been started 
with insufficient privilege, and so its tweak-the-clock requests are 
being silently ignored by the operating system.

If there is no drift file, the usual symptom is that the clock offset 
grows without bound almost linearly.

If there is a valid drift file, the usual symptom is that the clock 
offset sways more or less sinusoidally, this being the residue after 
the average clock drift is removed.


Joe Gwinn.