From: David VanHorn <microbrix@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Wed, 12 Aug 2020 15:09:29 -0700
Subject: Re: [EE] averaging multiple samples to reject AC interference
Thread-Topic: [EE] averaging multiple samples to reject AC interference
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" assuming the time it takes to aquire a sample is constant, how about
taking 3 readings A, B, C such that A and C are from the signal to be
measured and B is from the mains reference then the adjusted signal
becomes:"

is the shape of the AC line frequency what you're actually trying to remove=
?
Or is it a line frequency interference signal which is locked to the line
but not the same shape as the line waveform?


On Wed, Aug 12, 2020 at 3:25 PM sergio <smplx@allotrope.net> wrote:

>
>
> On Tue, 11 Aug 2020, Art wrote:
>
> > That's a great idea David, but with averaging, much performance is lost=
..
> > And, even without averaging, there is a finite propagation delay (phase
> > error) through the electronics-whether digital or analog.
> >
> > It occurred to me that I might use a second A/D converter to quantify
> > the 60Hz powerline frequency and apply that correction digitally. There
> > will still be propagation delay and the amplitude of the 2 data streams
> > will never match precisly, but the sampling of the realtime data can be
> > delayed and sync'd by some amount by delaying the digital clock time
> > sampling of one of the waveforms.?
>
> assuming the time it takes to aquire a sample is constant, how about
> taking 3 readings A, B, C such that A and C are from the signal to be
> measured and B is from the mains reference then the adjusted signal
> becomes:
>
> S =3D (A+C)/2 - B
>
> Since (A+B)/2 should correspond to the time when B was aquired
>
> Regards
> Sergio Masci
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