[time-nuts] 53230A noise floor

Tom Van Baak tvb at LeapSecond.com
Fri Apr 3 10:34:48 EDT 2015

> 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.


See the part the end that shows why averaging breaks ADEV:

> 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."


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