Filtering noise

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Joined: Tue May 11, 2021 10:29 am

Filtering noise

Post by marsheng »

I have a noisy signal but underneath the data is a reasonable curve. I'm new to digital filtering and was hoping for a hand on which filter to use and what components I need to download.

The chart required is the rate of change of speed of a drum. Its a dynomometer. Speed goes roughly from 45-65 kph and it is sampled at 30 hz over a 3-4 second run. The problem is that the speed change between samples is small hence the "noise."

Attached is the plot of speed (top) and rate of change of speed (bottom)
Plot.jpg (106.86 KiB) Viewed 4173 times
Any suggestions on how to go forward.

Delphi 6.

Thanks Wallace.
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Re: Filtering noise

Post by hlohning »

Without knowing any details it's hard to give an advice. However, in order to get a smoothed first derivative of the speed I would try to use a Savitzky-Golay smoothed derivative. See the procedure FirstDeriv for Details. You have to experiment with the WindowSize parameter.

Hans Lohninger
Epina GmbH
Retz, Austria
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