[time-nuts] LF power supply noise
magnus at rubidium.dyndns.org
Sun Jun 21 12:01:33 EDT 2009
> Hi Magnus,
> I was having the same problem with funny colors until I switched to
> LCD monitors. The problem went away:)
> I did try putting a large steel plate between the 543310A and the
> 2467B. The plate was 12"X12"X1/4" (30.48cm X 30.48cm X 0.635cm), and
> I checked it with a magnet to verify it was magnetic, but it had
> little effect.
Maybe it was not a suitable variant of steel. I used a pair of backsides
from a pair of 10 U Schroff racks, no particular steel at all, and it
proved useful to reduce the effects. Just as Bruce pointed out, steel is
not one thing, but magnetic permeability can change quite drastically,
so I just had good luck where as you didn't have such a good luck. Also,
aligning it properly for the field should increase the coupling effect
between the steel and the transformer... which is the important part.
> One of the reasons I was attracted to the 543310A was it could
> display 14 digits of frequency in one second. Sine then, I have
> figured a way to resolve 16 digits in one second, so that part of
> the spec is no longer interesting.
As was described by J. J. Snyder in "An Ultra-High Resolution Frequency
Meter" in the FCS 1981 (as available from IEEE UFFC) I assume, basically
using the fact that adding more measurements in a dense time raises the
degrees of freedom and allows for quicker interpolation.
Modern counters like HP 53131, HP 53132 as well as Pendulum CNT-90 or
Fluke 6690 uses similar approaches.
As being reported, such mechanisms does not fair well with ADEV
calculations, and especially the overlapping variants of ADEV and den
MDEV and TDEV which was inspired by that particular article, so using it
twice forms unwanted filters.
> The 543310A can do a single-shot time measurement with a resolution
> of 200ps, and gets down to 1ps with averaging. The HP5370B does 20ps
> single-shot, and will resolve 100fs with averaging. But I have
> figured a way to measure 2ps single-shot, and a bit better with
> averaging. So that part of the spec is not so interesting any more.
I assume you really mean HP 53310A and not HP 543310A, even if your
typing is consistent. The listed numbers is when weigthing in how
various jitter sources combine upon averaging and should be considered a
By all means describe what you mean by 2 ps single-shot resolution.
> The 543310A will display the phase and frequency changes in a PLL
> step response. But you can get the frequency response just by
> looking at the VCO DC error voltage. And if you look at the voltage
> across the bottom capacitor in a type 3 loop, you get the phase
> response. Here's a picture:
> -------------------------> to VCO
> --- C1
> |----------O < - Phase Error
> | |
> --- C2 \
> --- / R1
> | \
> | |
> --- ---
> - -
You should recall that when HP built their line of analyzers, they where
thinking "what can we make this cool ZDT core do?" rather than
attempting to build the best analyzer for all responsens.
> So about the only thing left of interest is histograms of the
> jitter. Unfortunately, the 543310A cannot store enough samples to
> really make an interesting graph. What I would like to be able to do
> is similar to an invention I made for the disk industry long ago,
> called Phase Margin Analysis. There is a brief description on my web
> page at
Somewhere in my map of apps there is a HP appnote for doing the same, to
discs, intended for disc industry, back in the days.
The HP 5372A and onwards (HP 5373A and HP 53310A) include hardware
histograms, to increase the rate of histogram builing. Use that rather
than the software more histograms. I don't know the details for the HP
53310A as I have never used one, but having a look at them it looks like
it also has the fast histogram measurement engine, which is also
described in detail by the patent... the HP 5371A did not have the
hardware histogram, so it uses software instead.
> There is a more detailed description in the paper, "Effect of
> Bitshift Distribution on Error Rate in Magnetic Recording", by Eric
> Katz and Tom Campbell, at
> But it doesn't look like the 543310A will be able to do that.
> Now that I can beat most of the performance specs of the 543310A, it
> doesn't seem worthwhile to spend much time trying to solve the
> problem of stray magnetic fields.
The 53310A was a nice convenient tool at its time, but it's performance
isn't up to spec with modern times. It seems like HP didn't pursue it
into much deeper levels after its VXI instruments, where as others went
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