Hi Chuck,
On 07/14/2015 07:46 PM, Chuck Harris wrote:
Hi Magnus,
Am I understanding correctly that the difference between Pi, Delta, and
Omega
is basically one of software processing after the sample is made?
Correct!
If so, how can this be best leveraged by those of us that have 5370A/B
counters
that are running John Seamon's enhanced BBB processor in place of the
original
5370 Motorola processor?
I would stream the raw samples over to the computer and do processing
there. Doing the Delta/Lambda estimation works if the computer side does
the right post-processing (which they rarely do).
Implementing this for "frequency only" in the BBB would not be too hard
if you like to do that.
I need to install my BBB board one of these days.
Cheers,
Magnus
Thanks!
-Chuck Harris
Magnus Danielson wrote:
Fellow time-nuts,
Since I haven't seen any reports on this, I though I would write down
a few lines.
While normal counters use a pair of phase-samples to estimate the
frequency, now
called Pi counters (big pi, which has the shape of the weighing
function of frequency
samples), counter vendors have been figuring out how to improve the
precision of the
frequency estimation for the given observation time. One approach is
to overlay
multiple measurements in blocks, which for the frequency estimation
looks like a
triangle-shape weighing, so this type of counter is referred to as
Delta counters
(again to resemble the shape).
Classical counters of the Pi shape is HP5370A, SR620 etc.
Classical counter of the Delta shape is the HP53132A.
However, counters using the Linear Regression methodology does not fit
into either of
those categories. Enrico Rubiola derived the parabolic shape of the
weighing function
(which I then independently verified after we spoke during EFTF 2014),
and he then
passed on the results to Francois Vernotte and other colleagues to
continue the
analysis.
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