Hello everyone,

I am needed to apply a filter to some acceleration data. That I think I can handle (I have chosen a Butterworth). What I do not understand are the CFC (Channel Filter Class) specifications. In particular, I do not know what a "Stop Damping" number specified in -dB is. Below is an example of a CFC60.

Filter type

CFC 60

Filter parameters

3 dB limit frequency: 100 Hz

Stop damping: –30 dB

Sampling frequency: At least 600 Hz

My sensor samples at 400 Hz which puts my CFC at about 36. Please correct me if I am wrong. At CFC 36, what would my parameters be? Do they define cut-off frequencies?

Thank you for any help. Google-skill"z" are failing me.

David

Edited August 23, 201213 yr by WCIGAFETW

I suppose it's the attenuation in the stop band. Your biggest difficulty seems to be that your software uses bizarre terms which are not the vocabulary of filter specialists. Also, to specify a low-pass filter, it needs the frequency where the stop band begins.

 

You should not take a Butterworth filter for acceleration data. At identical selectivity, it's the one with the worst step response: it rings (oscilates) horribly. Checychev is better, elliptic even better, and among known names, the inverse Chebychev (or type II Chebychev), minimum-Q-elliptic, and hourglass are good.

 

I know this is not the common opinion, but all other people are wrong because they compare at identical number of poles, while I compare at identical selectivity.