[time-nuts] Best counter setting for ADEV?

Bob Camp lists at rtty.us
Tue Oct 2 12:58:07 EDT 2012


Hi

By far the easiest way to do it with the combinations you describe is to do
a single mixer approach. Offset one oscillator by a few Hz and run the
counter on the beat note. You will need a mixer and a limiter, but the total
cost should be well below $100. If you have a pile of parts sitting around,
the cost could easily be $0.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Azelio Boriani
Sent: Tuesday, October 02, 2012 12:52 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Best counter setting for ADEV?

OK, so my 2.5nS resolution is OK. Now I have to determine what level of
average is best for the combination MV201/M12M and LPFRS/M12M.

On Tue, Oct 2, 2012 at 6:33 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> So to do things the "same way", start your time measurement at something
> less than 1 ms and do the math to get to 1 second and beyond. One
advantage
> over the frequency reading would be that you will know what math has been
> done. The math *does* very much matter....
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Tom Van Baak
> Sent: Tuesday, October 02, 2012 9:39 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Best counter setting for ADEV?
>
> 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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