Using a butterworth filter

Hi,

I have some experimental data (assume A). Those data were sampled at 0.5s. Now this data is pretty noisy, so I want to filter the data. I've read the butterworth filter is normally used to do this.

But now my question, cause I'm new to filtering. At what order and cut-off frequency should I use this filter and how should I implement it?

Thx!

Answer 1

[Jan]

The cut-off frequency and the order should be choosen base on the nature of the noice and the signal. At first an analysis of the noise is recommended: Which frequency and amplitude does it have? What is the nature of the wanted signal?

Imagine you want to measure the sea-level and use a laser to determine the height at specific times. You get noise from the limited precision of the laser system, perhaps water spots on the optical system, waves wither different wave lengths and the tides.

This is still not enough to determing valid filter parameters: If you want to measure the tides, you have to remove the high frequency signal. But if you wnt to measure the average height of waves with a certain wave length, a completely different filter will be needed.

Therefore your question cannot be answered in general.