Edson Brusque wrote:

> > As to RMS vs averaging, that's what the original question was about. =
 I
> just
> > didn't know if doing an RMS calculation had any benifits over just
> averaging the
> > input signal (better noise immunity, more accurate, more linear, etc.=
...).
>=20
>     RMS would give you a *more number.
>=20
>     Let's say you have a dimming application, where your circuit is
> connected to mains power @ 220V and you're firing the triac at 90=BA. Y=
ou're
> measuring the voltage going to the load. If you average your measuring,=
 it
> will say 110V. RMS will say about 155V. Now, if you rectify and "regula=
te"
> the energy going to the load (with full-cycle rectifying, 4 diodes and =
a
> capacitor) and measure it with a voltmeter, it will give you a value ve=
ry
> close to that 155V.


This is wrong, with 90' switching there is exactly
half the voltage average and half the rms voltage.
(and how do you make that "degrees" symbol??) :o)

So now i'm confused! Isn't RMS just calculating the
AC average?? I was taught that the only point to
squaring this and then doing a square root is that
this is only math way of making negative values
positive for averaging.

As programmers we have more power than mathematicians,
we are not limited to:
1. square it
2. average it
3. unsquare it

We can just do the following:
1. convert - values to +
2. average it

Or have I missed something?? Does anyone think we
MUST do square and square-root calcs in our PICs
and why??
-Roman

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