# [time-nuts] ADEV from phase or frequency measurement

Anders Wallin anders.e.e.wallin at gmail.com
Sat Mar 1 07:27:52 EST 2014

```Here is python code for the most common deviations
https://github.com/aewallin/allantools/blob/master/allantools/allantools.py

each statistic (ADEV, MDEV, TDEV, and so on) has two functions. one takes
fractional frequency data, the other phase data. frequency2phase() and
phase2freqeuncy() show how the conversions are done.

Anders

On Sat, Mar 1, 2014 at 1:37 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> Hi Volker,
>
> Either phase or frequency raw data can be used to generate an ADEV plot,
> but you have to use different methods depending on the data type.
>
> See the two formulas for Allan Variance in:
> http://www.wriley.com/paper2ht.htm
>
> Usually we use the "x" form of the formula, where x is an array of phase
> samples. But if you have frequency samples then use the "y" form instead,
> where y is an array of frequency samples.
>
> Note you can also convert phase data to frequency data (by
> differentiating) and use the "y" form. Or convert frequency data to phase
> data (by integrating) and use the "x" form.
>
> /tvb
>
> ----- Original Message -----
> From: "Volker Esper" <ailer2 at t-online.de>
> To: "Discussion of precise time and frequency measurement" <
> time-nuts at febo.com>
> Sent: Saturday, March 01, 2014 3:15 AM
> Subject: [time-nuts] ADEV from phase or frequency measurement
>
>
> > Hello dear fellow time-nuts,
> >
> > I stumbled over a question that may sound stupid to you:
> >
> > Is the usual ADEV plot the result of a phase or a frequency measurement?
> >
> > I get totally different results when comparing a phase and a frequency
> > measurement of the same source. Or am I doing something totally wrong?
> >
> > Thanks a lot
> >
> > Volker
>
>
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```