Butter Filter Cutoff Frequency?

[jcannon]

Hi everyone,

This is a really basic question, by just needing confirmation.

When using the butter filter vi are the high and low frequency cutoffs absolute frequencies or normalised frequencies? I assume absolute based on the help information but the default values are 0.125 and 0.450 are very small, which might represent normalised frequencies.. 

So, if my signal sample rate is 2000Hz and I want to implement a bandpass filter between 20-500Hz, can I simply use 20Hz and 500Hz as my low and high frequencies or should I use (20/2000/2= 0.02) as my low freq and (500/2000/2= 0.5 Hz) as my high freq?

Thanks for any input.

Regards,

Jack

[GerdW · Accepted solution]

Hi Jack,

the help clearly mentions "frequency in Hz" for all 3 frequency inputs…

[jcannon]

Thanks.