Re: Wanting a circuit to find the average of a fluctuating DC signal ???
- From: "Thomas Magma" <somewhere@xxxxxxxxxxxxxxxxxx>
- Date: Wed, 23 Jul 2008 16:43:26 GMT
<jalbers@xxxxxxx> wrote in message
news:841c4ffa-5ab4-4bd7-bdd6-0e9e59dd320d@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I am looking for a circuit that will give me the average of a
fluctuating DC signal. I am using the term average to roughly mean a
value in the middle but doens not have to be exact.
A few years ago I was told by some people in this group to simply use
a low pass filter. At that time I did not have the equipment, time,
or knowledge of filters to mess with it. I have started to play
around with different types of filters...
I have done a little bit of experimenting using a scope, signal
generator, and a simple low pass RC filter but can't get it to work to
find the average of the signal.
I am ultimately interested in averaging the fluctuating DC signal from
a homemade EDM machine which is a basically a big DC relaxation
oscillator. For various reasons, I do not want to use the actual EDM
machine for these experiments. I have been using a function generator
and also a NE-2 relaxation oscillator to somewhat simulate the signal
that the EDM machine is going to be putting off. I have experimented
with sine, triangle, square, and relaxation oscillator wave forms with
enough DC offset to push the entire waveform completely up above the x-
axis on the scope. To no surprize, increasing the frequency begins to
attenuate the signal and the output of the low pass filter starts to
hug the x-axis. The capacitor is removing the DC component and
attenuating the AC part of the signal.
I don't think that a LC low pass filter is going to work the way I
want it to either. It will not remove the DC component but the
waveform will still hug the x-axis.
I am looking for something that will attenuate the signal as the
frequency increases but still keep the DC component of the signal.
Any help would be greatly appreciated. Thanks
A capacitor in a low pass filter shouldn't be removing the DC component, by
definition it is just the opposite. What voltages and frequencies are we
talking about here? And what is this x-axis you are talking about?
How about a simple RC filter?
Thomas
.
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- From: jalbers@xxxxxxx
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