- Dec 9, 2001

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Let's say I'm trying to measure a DC signal. The oscilloscope picks up some noise in the signal and I get discrete points for data. I can apply a digital filter with my software to filter out some of the noise, but I want to know which frequency to apply it. I'm assuming this digital filter is some algorithm written to behave like a bandpass filter, but I'm not 100% sure.

I know for a continuous function, I can apply FT to convert everything to frequency domain to see where the noise is. If I do DFT to a discrete set of collected points, I'll turn the points into the frequency domain...

That's fine and all but how do I pick out which frequency is which from only discrete points? Obviously the points will have a time associated with it, but this is kind of beyond my field of expertise.