[time-nuts] Allan Deviation recipe?

Tom Van Baak tvb at LeapSecond.com
Mon Jul 18 22:40:08 EDT 2016

> Got some C or Python?

See Anders Wallin's post: https://www.febo.com/pipermail/time-nuts/2014-March/083298.html

For C, I use adev4.c and adev5.c under www.leapsecond.com/tools/ when I don't need the interactive power of TimeLab or Stable32 or when I'm working with millions of data points. Then I use Excel or gnuplot to make the log-log plot. After much trial and error here's a gnuplot example:


Perhaps PHK can comment if Dave Mill's terminology wrt Allan deviation is strictly correct or not. There's Allan variance, and Allan deviation (which is just its square root). Then less-rigorous usages like Allan intercept or Allan floor, etc. Be careful with your interpretation since AFAIK NTP is working only with past+present data rather than a complete past+present+future data set.


----- Original Message ----- 
From: "Gary E. Miller" <gem at rellim.com>
To: "Tom Van Baak" <tvb at LeapSecond.com>
Cc: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Monday, July 18, 2016 7:01 PM
Subject: Re: [time-nuts] Allan Deviation recipe?

Yo Tom!

On Mon, 18 Jul 2016 18:42:39 -0700
"Tom Van Baak" <tvb at LeapSecond.com> wrote:

> Lots of ways to do it. There are GUI tools; command line tools, in C
> or Python or Matlab.

Got some C or Python?

> But to start with I highly recommend using John's TimeLab:
> http://www.ke5fx.com/timelab/readme.htm

I don't do Windows...  And I want this to auto-generate graphs for web
pages on RasPi's.  Lot's of RasPi's.  :-)

> Here's a sample 1PPS phase (time interval error) data file (from a hp
> 53132A): http://leapsecond.com/pages/MG1613S/log167.txt

Yeah, that looks sorta like what I have.

> Or here's the same file in a more standard format:
> http://leapsecond.com/pages/MG1613S/log167.dat

Just the facts there, i can do that.

> http://leapsecond.com/pages/MG1613S/log167-adev.gif

That's what I think I am looking for.

A bit of background.  Ntpd generates a number they call the Allan
Deviation, but the description looks like the Allan Variation, they
describe is as the minima in the Allan Deviation plot, when it has a U

They then use that number to set the PLL optimally.

Something looks fishy to me, so I want to visualize it, and help the
rest of the NTPsec team see it as well.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
 gem at rellim.com  Tel:+1 541 382 8588

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