At 12:15 AM 3/23/00 -0500, you wrote:
>Back on the topic of measuring an analog signal and calculating RMS, I'm
>stuck on a certain thought.
>If I take 255 or 256 readings that are all read exactly at the peak of 255,
>and I accumulate a sum of squares of 255, then divide by the number of
>samples and take the squareroot, I'm left with 255...which is the peak
>value...
>So how can that be RMS?

You have discovered 'aliasing', you need to get many more samples than
one per cycle. If the input is DC, you would get each measurement the
same, and the RMS value *is* the same as the peak value for DC.

Best regards,




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Spehro Pefhany                                    "The Journey is the reward"
speff@interlog.com
Fax:(905) 271-9838                      (small micro system devt hw/sw + mfg)
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