BioSemi.nl

I recently started using the ActiveTwo BioSemi and was using a sampling rate of 2048Hz. However, I am wondering if it is possible to change the sampling rate to anything I want (preferably 1000Hz) as it makes it easier for me to downsample to 250Hz in my analysis. I found on the BioSemi website that the ActiveTwo system has sample rate options of 2, 4, 8, or 16 kHz per channel and I’m using 64 channels. Does that mean I can only sample at 128, 256, 512, 1024 or 2048Hz? I also found on another website that it has to do with the Decimation Ratio which relies on the AD and speedmode. I’m not sure how this all relates to each other and would love to have a better understanding.

Only integer divisions or multiples of 2048 Hz are possible. Sample-rate are available in powers of 2 from 32 Hz (speedmode 4, decimation = 1/64) to 16384 Hz (speedmode 7, decimation = 1).

Note that the analog bandwidth is always approx. 1/5th of the sample-rate (indicated in the right sidebar). For example: at 256 Hz sample-rate the anti-aliasing filter kicks in at approx. 50 Hz. So, do not choose a sample-rate too low or you may loose higher frequencies (generally, sample-rates below 512 Hz are not used for EEG).

Best regards, Coen (BioSemi)