[time-nuts] 53230A noise floor

jpbridge at aol.com jpbridge at aol.com
Fri Apr 3 17:22:17 EDT 2015


I've just been playing with my new (ex demo) fca3100 and the results seem dependent on setup.
(I'm not trying to hijack the thread from the 53230A but I think it is useful to have comparison results - I know I would have liked to see some prior to buying my counter.)

I have found that if I turn off the interpolation calibration then the std figures drop significantly at a bit of a cost in skew between channels.

Changing the impedance to 50 ohms from 1Mohm and doing the experiments with the instruments own pulse generator (though results with my separate pulse generator aren't hugely different) I get the following:

A->B no calib  std : 19 ps mean (1M) : 1.285 02 ns
A->B calib       std : 29 ps mean (1M) : 1.286 55 ns
B->A no calib  std : 20 ps mean (1M) : 1.298 00 ns
B->A calib       std : 31 ps mean (1M) : 1.292 63 ns

with this setup the difference between calib on and off is only -1.53 ps or + 4.63 ps (for other setups
it is rather larger).
The difference from A->B vs B->A is only 6 ps with calib on and 13 ps with calib off.

I don't know quite what to conclude from all this other than being careful about signal shape and matching and setting of trigger levels can improve results significantly.

Secondly, there seems to be a trade off between channel skew and single shot resolution - I have no idea why as I'm not sure what the interpolator calibration does -  but if this is general perhaps Keysight have geared the 53230A to give low single shot resolution at the expense of slightly higher channel skew.

James



 

 

 

-----Original Message-----
From: Anders Wallin <anders.e.e.wallin at gmail.com>
To: Discussion <time-nuts at febo.com>
Sent: Fri, 3 Apr 2015 12:04
Subject: [time-nuts] 53230A noise floor


Hi all,

I ran some tests on a new 53230A counter that just
arrived:
http://www.anderswallin.net/2015/04/keysight-53230a-noise-floor-test/

The
time-interval single-shot noise and resulting ADEV seems easy enough
to
explain.

I didn't yet have time to look closely at Enrico Rubiola's notes
over here:
http://rubiola.org/pdf-slides/2012T-IFCS-Counters.pdf
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.

on another note:
The
discussion on phase-noise <-> ADEV calculations earlier was
interesting.
Datasets (synthetic or real) with known correct ADEVs and
phase-noise-spectra
would be a good addition to allantools and a motivation
to add code for the
phase-noise <-> ADEV
conversion.

cheers,
Anders
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