Re: Electrical signal analisis

[Joe Koski]

on 8/21/04 11:10 AM, robert Macy at address@hidden wrote:

> 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 -
> 
Robert,

I just tried and downloaded the full UNIX tftb.tar.gz version from the
mirror site without any problems. I did not try the .zip version or the main
site.

Joe Koski 


> 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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>> GPL.
>> 
>> Octave's home on the web:  http://www.octave.org
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> 
> 
> 
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
> 
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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