[mathcad] Re: DSP method

Author: Richard Jackson Posted: Wed, 11 Jan 2006 14:22:52 -0500

Without seeing the data I have to guess a bit, but you could fit a spline
to one data set, so that it is represented by a function, f(x). Then least
squares fit f(x-delta) to the second data set, with delta as a parameter.
You will probably not be able to use the all the data though. Assuming
the two data sets are the same length, if you shift one relative to the
other parts of them will not overlap. You can use only the overlapping
sections.

A variation would be to also fit a spline to data set 2, to generate a
function g(x'). Then simultaneously fit g(x'-delta) to data set 1 and f(x-
delta) to data set 2.

Richard

On 11 Jan 2006 at 17:26, Mark Smith wrote:

>
> I have 2 digitised signals (A2D sampled) which are very similar in
> shape but differ by a fixed time difference, can anyone suggest
> methods which will allow me to calculate what the time difference is?
> I have thefeeling that if i can somehow use all the data I should get
> a much more accurate value than say just comparing a zero crossing of
> the 2 traces which I think will be far more susceptable to noise in
> the signal.
>
> Thanks in advance
> mark

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