Biosignal filtering

[dan23]

Hello,

I try to use Biosignal filtering from Biomedical Toolkit. Unfortunately, I am not able to set the filter as bandpass between 0,5 and 100 Hz. My sampling frequency is 200 Hz. 

Thank you,

Daniel

[Bob_Schor]

You might be "doing something wrong", but it is difficult to guess what this might be without your posting your code so we can see what you are doing.

What do you know (from Signal Theory) about sampling frequency, total sampling time, # of points sampled, and the maximum and minimum frequency present in your signal?  [I'm guessing the answer is "not very much", as you specified a band-pass of 0.5 to 100 Hz and a sampling rate of 200 Hz -- do you see what is curious about this?].

Bob Schor

[dan23]

I already solved it. Thank you for the inspiration what could be wrong. 

[AryaStark92]

Hi,

May I know how you resolved it? I am facing the same issue. Not sure about the frequency of the incoming bio signal.

Thanks,

Geetha

[JÞB]

Read THIS! 

Now we need to speak about Nyquist Frequency and Frequency Resolution

Frequency resolution (the smallest change in Frequency that can be detected) is 1/ record length.  Basically you need 2 seconds of time record to get 0.5hz resolution.   To detect DC you need an infinite time.

The Nyquist Frequency is 1/2 of the sample Frequency e.g. if you sample at a constant 1khz you can detect frequencies up to 500hz without aliasing (Frequency components greater than 500hz will be "Folded.")