[time-nuts] ADEV query Timelab and TICC

Tom Van Baak tvb at LeapSecond.com
Mon Mar 20 00:00:43 EDT 2017

Hi Orin,

More info... If you try to manually remove the 25 ns glitches you get a data set that looks much better. Attached are the ADEV plots for (1) your raw data and (2) your data minus those 8 glitches. You can see the dramatic difference that just 8 points make. Blue is raw data, red is data without those 8 glitches.

Now, this is not likely your fault. Also, I'm not saying we know yet what causes the glitches. This posting is merely to show how 8 bad points out of 8,000 points can totally mess up an ADEV plot.

And without preaching too much, this is why I recommend no one does statistical work (e.g., ADEV) without first looking at the raw phase and frequency data. A doubting Thomas attitude and the human eye are valuable tools in science. Both Stable32 and TimeLab make it easy to display phase and frequency, not just ADEV. This is not by accident.

Maybe we have hyped ADEV too much on this list. This rant is especially addressed at several LH and NTP authors who think analyzing clock data and making ADEV plots is just something you blindly code or script or automate, as if working with clock measurement data was as pure as mathematics.

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