[time-nuts] Best counter setting for ADEV?

[Azelio Boriani]

OK, got the papers. I'm still trying to figure out if a minimum resolution
can be determined for the TI measurement OCXO_PPS/GPS_PPS. That is, if the
GPS has a 25nS random wondering, is it worth having 25pS measurement
resolution? At first yes, I can use the negative sawtooth but I'm not
convinced. Then, I'm using a simple average over 100 or 1000 seconds but my
OCXO moves menawhile: the simple average is not the ideal tool and I'm
still investigating what magical statistic can I use.

On Tue, Oct 2, 2012 at 3:39 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> Azelio,
>
> In frequency average mode the 53132A makes something like 200,000
> measurements per second, according to the manual. This is why the
> instrument does so well as a smoothed frequency counter. The resolution
> "gain" is some fraction of sqrt(200000), subject to the normal caveats like
> the need for independent samples. That's why these counters have reduced
> resolution when the input frequency is too close a multiple/fraction of the
> timebase.
>
> Details on this technique (used also in the Pendulum CNT-9x counters):
>
> "New frequency counting principle improves resolution"
> http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf
>
> See also this fine presentation by Staffan Johansson:
> http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf
>
> Or, google for: continuous time-stamping frequency counter
>
> /tvb
>
> ----- Original Message -----
> From: "Azelio Boriani" <azelio.boriani at screen.it>
> To: "Discussion of precise time and frequency measurement" <
> time-nuts at febo.com>
> Sent: Tuesday, October 02, 2012 5:30 AM
> Subject: Re: [time-nuts] Best counter setting for ADEV?
>
>
> > Hmm, the frequency mode sigma is the same as the TI mode sigma for
> 200*tau.
> > That is if I take the sigma at 200*tau from the TI mode I have the same
> > figure of the frequency mode. Maybe the frequency mode 2 seconds sample
> > time uses 100 averages per second.
>
>
>
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