[time-nuts] Long period variation of GPS PPS timing?

Joseph M Gwinn gwinn at Raytheon.com
Thu Jul 1 13:19:58 EDT 2010


time-nuts-bounces at febo.com wrote on 07/01/2010 12:06:54 PM:

> From:
> 
> Paul Nicholson <vlf0308 at abelian.org>
> 
> To:
> 
> Discussion of precise time and frequency measurement 
<time-nuts at febo.com>
> 
> Date:
> 
> 07/01/2010 12:08 PM
> 
> Subject:
> 
> Re: [time-nuts] Long period variation of GPS PPS timing?
> 
> Sent by:
> 
> time-nuts-bounces at febo.com
> 
> Thanks all for the various replies, on and off list.
> 
> John WA4WDL wrote:
>  > Perhaps you should use only the leading edges for the
>  > pulse-to-pulse interval measurement.
> 
> Yes, I'm just using the leading edge, turning it into a pulse
> using a couple of RC networks, slowing the rise and fall enough
> to give a nice shape for accurate locating of the centroid.

The centroid of pulses triggered by the leading edge of the 1PPS pulse 
will vary with the width of the pulses.  If you are using a non-precision 
pulse generator, many things can affect the apparent locations of the 1PPS 
pulses.  Like changes in temperature and/or supply voltage.

Joe Gwinn




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