[time-nuts] Modified Total Deviation measurement
Magnus Danielson
magnus at rubidium.dyndns.org
Mon Jan 18 06:16:50 UTC 2010
Hi Dick,
Dick Moore wrote:
> Hi Magnus -- Any possibility that there is some math package subroutine error of some kind? In yours or theirs?
Well, wherever the error is, for a known series of 1000 frequency
samples (or equalent 1001 time samples) I expect the error to be
algorithmic rather than math-support. Programming in crisp C gives me
the floating-point processor and only the sqrt may be affected and
numbers sits nicely there, no great cancelation in the big sums (they
sum up squared values) so no, it is not very likely.
The modified total deviation involves taking 3*m samples out of the
sequence, calculate the frequency of those samples, compensate the
samples, mirror them up and down in non-inverting even mirroring to 9*m
samples, preform the tripple-diff of the second derivate and average
over m samples. A couple of sums, averaging and scaling terms. There are
many small details that could go wrong. For instance, I can't understand
how the Hadamard Total Deviation for m=1 is equal to the Hadamard
Deviation for m=1. The inner sums comes out differently for
back-of-printout pen-and-paper analysis. Something is fishy here. Either
I am quite stupid or...
Cheers,
Magnus
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