[time-nuts] Best counter setting for ADEV?

Tom Van Baak tvb at LeapSecond.com
Tue Oct 2 09:39:12 EDT 2012


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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