[time-nuts] 53230A noise floor

Ole Petter Ronningen opronningen at gmail.com
Tue Apr 7 07:44:17 EDT 2015


Tangetially relevant; I made a "patch" for TimeLab to use the gap-free
frequency measurement-mode for the 53230A, if anyone is interested.

On Fri, Apr 3, 2015 at 4:34 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> > There is probably a good explanation for the ADEV-level in standard
> > (pi-counting?) reciprocal frequency counter mode as well as the roughly
> > 1/sqrt(10) enhancement in ADEV when increasing the gate-time 10-fold.
>
> Anders,
>
> See the part the end that shows why averaging breaks ADEV:
>     http://leapsecond.com/pages/adev-avg/
>
> > I collected the data with a simple program that just calls the "READ?"
> function
> > repeatedly, which does result in some dead-time between measurements.
>
> Yes, that's the easy way. But for more valid results use gap-free
> continuous mode (SENS:FREQ:MODE CONT). From the manual:
>
> "CONTinuous configures the instrument to make continuous
> resolution-enhanced, gap-free measurements.  This mode should be selected
> for true Allan deviation computation (CALCulate:AVERage subsystem).  In
> this mode, all samples for a each trigger are started by a single gate open
> (instead of gate open/close per sample), and the measurements are computed
> back-to-back with no dead time.  CONTinuous can only be used for frequency
> and average period measurements. Available only on the Agilent 53230A."
>
> /tvb
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