BioSemi.nl

Hi BioSemi experts,

I have (maybe a weird) question: If I run two subjects simultaneously connected to the BioSemi amplifier (two caps with 64 electrodes each connected to the 4 slots, 2 per each subject), can I use one subject to be used as a ground where CMS/DRL electrodes are connected and the other without the ground electrodes? Is this theoretically possible, if so, what are the practical consequences?

Best,
BAris

The setup proposed above will not work because of the lacking CMS/DRL connection of the second subject (no signal from the electrodes of the second subject).

For simultaneous measurement of up to four subjects, we offer the "daisy chain" option, also see http://www.biosemi.com/new.htm , and scroll down to 26 Sept 2005). A separate AD-box is used for each individual subject, each with its own CMS/DRL connection. The AD-boxes are set to speedmode 0 (subject 1) to speedmode 3 (subject 4), see http://www.biosemi.com/faq/adjust_samplerate.htm . The AD-boxes are daisy chained by optical fibers: Box1 --> Box 2 --> Box 3 ---> Box 4 ---> USB receiver. All data for 2, 3 or 4 AD-boxes is processed by a single PC running standard ActiView. All data (maximum of 4 * 128+8+8 channels on 2 kHz) is saved in a single BDF file. The sampling of all AD-boxes is synchronized via the optical connections. The subjects remain complete galvanically isolated from each other (just optical fiber connections between the subjects), which ensures optimal interference reduction and safety. If necessary, the distance between the subjects can thus be extended to hundreds of meters.

Best regards Coen (BioSemi)