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Re: gEDA-user: RMS Waveform of a signal



Never mind, I use free gEDA as well (in the hope) to do professional work
and I shamelesly ask it to be even better than commercial.
To answer your question: as can be seen from the definitions given at

   http://en.wikipedia.org/wiki/Root_mean_square

a rms-function can be defined in two ways:

a) non-continuous as the sequence of points describing pieces between adjecent
  extrema of the input signal

b) continuous as a moving average with a fixed integration interval delta_t

If a) is used I assume a spline is used to fake a continous function, but
it's more likely to see b) used, which of course requires some voodoo to
determine delta_t. It's exactly this which I don't like about commercial ;-)

Armin


Rubén Gómez Antolí wrote:
Hello Armin:

Thanks for your response.

El 16/06/10 15:16, Armin Faltl escribió:
To the best of my knowledge, the RMS-value (root mean square) is a
constant,
i.e. the waveform would be a straight horizontal line. The definition of
the value comes from power considerations: it's the constant
current/voltage
that produces the same power(-dissipation) as the signal.

I'm not completly sure but, these are true when the signal is regular and periodic.

If you have a "strange" wave, you get a time-variant rms wave. Look a example on top of page 3 in this PDF:

http://fie-conference.org/fie96/papers/219.pdf

(plot RMS(i(r)))

Armin

Sincerily, I thought that this are more usual, but there are very few references on web and nothing in how to obtain in "free world" (at least, I can't find it).

Best regards.

Salud y Revolución.

Lobo.


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