Notch filtering between 45 and 55Hz?

Hi everybody,

I'm wondering whether it is an advantage to notch filter the line noise from 45Hz to 55Hz? Or is it enough to just filter out 50Hz?

I'm currently using a 2nd order Butterworth filter and the data is from Europe.

Best,

Eric

Answer 1

[Star Strider]

It depends on your signal. I would do a fft on it to see how wide your sampled 50 Hz signal is, since that reflects an interaction between your actual signal and your ADC hardware. (The line frequency is reasonably stable but does vary slightly.) Then design your filter to notch-out the mains signal, but as little of your desired signal as possible. (I always use the ‘sos’ implementation, and check my filters with freqz to be sure they do what I want them to do.)