Lowpass filter
Posted: Thu Jul 09, 2020 12:55 pm
Hello!
I'm a bit confused about the lowpass filter settings used during recording. I have an ActiveTwo amp, and I usually set the speed dial mode to 4 (sampling rate 2048Hz). In ActiView, I select a decimation factor of 1/4 to get signals with a sampling rate of 512Hz.
According to your website, the cutoff frequency of the hardware lowpass filter is 1/5 of the sampling rate, so 2048Hz / 5 = 409.6Hz for my setting. After decimation, this should be 409.6Hz / 4 = 102.4Hz. However, the BDF file headers contain a field with "LP: 104Hz" (which is also what ActiView shows for the bandwidth).
What is the correct cutoff frequency?
Thanks,
Clemens
I'm a bit confused about the lowpass filter settings used during recording. I have an ActiveTwo amp, and I usually set the speed dial mode to 4 (sampling rate 2048Hz). In ActiView, I select a decimation factor of 1/4 to get signals with a sampling rate of 512Hz.
According to your website, the cutoff frequency of the hardware lowpass filter is 1/5 of the sampling rate, so 2048Hz / 5 = 409.6Hz for my setting. After decimation, this should be 409.6Hz / 4 = 102.4Hz. However, the BDF file headers contain a field with "LP: 104Hz" (which is also what ActiView shows for the bandwidth).
What is the correct cutoff frequency?
Thanks,
Clemens