Yo Hal! On Tue, 19 Jul 2016 14:28:32 -0700 Hal Murray <[email protected]> wrote:
> [You sent that to 3 lists that I'm on. I'll reply here. Yeah, but time-nuts is the one list that knows more about this than I do. So good choice. > I think your X axis is off. Your left edge is 1 second and you don't > have data for that. peerstats is every 64 seconds. (unless you > mucked with maxpoll) I'm guessing the software you used is assuming > they are every second. There may be a command line parameter. I'm taking the time and offset from the /var/log/ntpstats/peerstats file. So the data is collected every minpoll (16 seconds), timestamped in seconds with millisecond precision. The offsets are also in seconds. Should I set the left edge to 16 seconds? > The normal ADEV is V shaped. The left slope is noise in the > readings. The right slope is drift in the clock. That assumes you > have a good reference clock, where good means much better than the > DUT. Well, the data is the data. I used Tom Van Baak's adev5 program to do the calculations. Given that the system is GPS stabilized on PPS I can't see why the accuracy should not get better over long durations. > In this case, there is no long term drift since ntpd is tracking > GPS. You will probably get a traditional V if you disable ntpd. Well, I'm trying to measure ntpd, so chicken and egg here. > There is a slight step in the NMEA data at 1000 seconds and maybe a > similar step in the PPS data at the right edge of the graph. I don't > know what that means. At Tom's suggestion, I upped the sampling from Octaves to 50/decade. I also added TDEV. Now there is some structure in there. https://rellim.com/graphs/adev.png Some weird things in there... RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 [email protected] Tel:+1 541 382 8588
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