>>> ok, my idea was to make this peak-measurement every 20mS,
>>> and average it with the previous one. Resimulated the peak
>>> method, and it fits in the 1.2% error indeed.
>>
>> You are still sampling at 1KHz to find the peaks, right? =A0The
>> 1.2% error I mentioned comes from the 1KHz samples missing
>> the peak by as much as 500uS.
>
> Yes, my (and your) simulation show that.


Detecting peaks is not a good idea in my opinion. Much better advice was:


> Trying to detect the peak value and scale that is IMO a bad idea
> because a single brief spike could throw the reading way off.
>
> Taking the average of the magnitude and scaling it would probablly
> be a reasonable option. True RMS is also pretty easy to calculate
> (square the individual values, average them and take the square root
> at the end)

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