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Re: Electrical signal analisis


From: robert Macy
Subject: Re: Electrical signal analisis
Date: Sat, 21 Aug 2004 10:10:08 -0700

Group (and Joe)

  http://iut-saint-nazaire.univ-nantes.fr/~auger/tftb.html
The URL at France didn't seem active.  Any new location for
same information?

       - Robert -

On Wed, 18 Aug 2004 10:30:45 -0600
 Joe Koski <address@hidden> wrote:
> There are two more signal processing libraries (besides
> those with octave
> and octave-forge) of which you should also be aware, and
> possibly install.
> The URLs for them are
> 
> http://www-stat.stanford.edu/~wavelab/
> http://wiki.octave.org/wiki.pl?WavelabOnOctave
> 
> And 
> 
> http://iut-saint-nazaire.univ-nantes.fr/~auger/tftb.html
> http://perso.ens-lyon.fr/patrick.flandrin/emd.html
> 
> The latter has a routine extr.m that finds all local
> maxima and minima of a
> time (or frequency) series.
> 
> For help with octave and octave-forge signal processing
> routines, check the
> information at 
> 
> http://octave.sourceforge.net/index/index.html
> 
> There is a wealth of good signal processing software
> available. Good luck.
> 
> Joe Koski
> 
> on 8/17/04 7:10 PM, Jaime Alberto Silva at
> address@hidden wrote:
> 
> > I'm new in the use of this tools (octave, mathlab,
> etc.) and since I'm a
> > full time Linux user I am using octave.
> > 
> > Currently, I'm trying to do some electrical signal
> analysis and I will
> > like to know if there are predefined functions for some
> calculations or
> > how can I do them with octave:
> > 
> > 1. Frecuency: I have founded in the "Signal Processing"
> section the fft
> > function, OK it is great but how do I find the
> frecuencies from the
> > returned vector. I know that using the max function I
> can find the
> > fundamental frecuency like this:
> > 
> > # Create the signal:
> > octave:190> t= [0: 1/2000: 5 - 1/2000];
> > octave:191> sint= sin(2*pi*60*t);
> > # Transform the signal:
> > octave:192> ft= abs(fft(sint));
> > # Find the position of the max value of the
> transformation:
> > octave:193> [val, idx]= max(ft);
> > # Use the sampling rate to obtain the fundamental
> frecuency:
> > octave:194> fund_frec= 2000 * idx/ length(ft)
> > fund_frec = 60.200
> > octave:195>
> > 
> > But how can I find the other frecuencies in case it has
> more components
> > like in
> > f= sin x + 0.5 sin 3x + 2 sin 10x ?
> > 
> > 2. Phasors: If I have 2 signals like v1 an v2 how do I
> find the angle of
> > v2 with respect of v1. I mean if v1= sin (t) and v2=
> sin (t + 15°) and I
> > have sampled those signals in time, how do I find that
> v2 is delayed 15
> > degrees with respect to v1? taking in account that v2
> samples where
> > taken in different times to v1 samples like this: v1(1)
> was taken at T0,
> > v2(1) was taken at T0 + dT. And, of course, you know
> the value of dT.
> > 
> > 3. Electric Power: If I have sampled the signals of
> voltage (V) and
> > current (I) are there any tools that l can use to
> obtain the active (P)
> > and reactive (Q) power, the S vector angle, etc. ? I
> know that I can
> > multiply the signals but, you know if there are tools
> for that why do it
> > again.
> > 
> > Thanks in advance for any help you can bring me.
> 
> 
> 
>
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