BioSemi.nl

Hi,

I am working with a BioSemi Active 3 system with 64 channels with a GSR module. I tried recording EEG + GSR of three participants. For 1 out of those three I get 16Hz oscillations in all channels (see attached), for the other 2 I get 16Hz oscillations in 1 channel only (P1 and P2, respectively). In old posts I read that this 16HZ interference is normal with the DRL on the head, and that it can be removed with a sharp notch filter on 16Hz. Alternatively, it can be reduced by having the DRL between the hand and head. I have two questions I hope you might be able to help me with:

1. Do you have any idea as to why 2 out of my 3 participants show this 16Hz interference only in 1 channel, while the third participant has the 16Hz oscillations in every channel?
2. For an alternative DRL location (e.g. the neck) I suppose I would need a flat-DRL/pin-CMS. Is this currently available?

Thanks very much in advance!
Julie

It looks like a combination of a defect GSR sensor (most probably a short circuit to the isolated 16 Hz oscillator) and a gel bridge between DRL and P1/P2 (in the cases were only one channel shows 16 Hz). Please sent the GSR sensor to BioSemi for checking and replacement.

Best regards, Coen (BioSemi)