Hi Chris!

Years ago,I have worked with a Hewlett-Packard's "True RMS voltmeter"  .
This instrument can measure RMS value from DC to 30 MHz from
arbitrary waves (not only senoidal).

The principle of measuring was a kind of retroalimentation system:
one branch of the system is heated by input signal, and the other
by a DC current. In fact, the A/D converter only reads the DC
needed to balance the system.

The heat to voltage converter was two paired transistors;
each transistor has a heating resistor.All integrated in a IC.
Increasing temperature will down Vbe.
If the input signal increases, the heating resistor number 1
heats the first transistor.

The Vbe of the first transistor decreases; then, a operational amplifier
senses this Vbe variation  and increases the DC current of the other
heating element.
This action down Vbe of the second transistor.
Finally, the system achieves a balanced state. Current in heating resistor
number 2 was proportional to the RMS value of input signal.

Well, perhaps this is no applicable to your idea...But analog computing
techniques are fast; may be you can use an analog multiplier in
order to obtain the square of the input signal, or integrate
the wave with a amp-op . Amp-ops of today are very fast.
Once a DC representation is obtained, the PIC can "do the math"
with it.

Or, make your own full adder using a FPGA ! :-)

Cheers!

      Alejandro.

At 19:55 21/03/01 -0500, you wrote:
>Folks, I need to perform an integration on a complex wave.  It is too
>fast to use the PIC A/D directly, as the 50+KHz complex waveform will be
>converted at say 500KHz.  I plan to use an A/D converter and then create
>some sort of full adder after that.  I must make it work for signed
>values.
>
>The goal is to accurately measure energy in Joules.
>
>Does anyone know of any device which does this?  If there is no such
>device, I will have to go the CPLD or FPGA route.  If I do, does anyone
>have any good advice for me??
>
>When the full adder rolls over, I will catch the results with my PIC.
>
>Chris Eddy~
>
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