[time-nuts] Running voltages through MVAR (In re: HP5065)

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Aug 23 15:25:36 EDT 2015

In message <85E3D5A82F314700BCA6493EEF245CCF at pc52>, "Tom Van Baak" writes:

>1) The scale is more intuitive, I find, when sqrt is used -- so I'm curious why you chose MVAR instead of MDEV?

Actually the plot is MDEV now that I think of it...

I've added a footnote.

>2) When plots mostly head down with a -1 slope, consider TDEV
>instead of MDEV, which effectively rotates by 45 degrees turning
>-1 slopes into 0 slopes. For some kinds of data a rise above a
>normal (zero) slope is more informative than a bend of a steep -1
>line. Psychologically too, it removes the
>"things are working better and better as time goes on" impression
>that happens with a -1 slope, e.g., when ADEV is used on data from
>a locked loop.

Good point.

>3) Before you settle on MDEV, also try ADEV. There are cases where
>the massive averaging inside of MDEV ruins interesting noise periodics

I generally hunt periodics with FFTs, but yes, ADEV is useful for the
sort of "almost has a stable frequency" like HVAC's turning on/off etc.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

More information about the time-nuts mailing list