DC offset rising to the sky

[mihaela.grigore]

Dear BioSemi support,

I would like to ask for your advice on an issue I had today. It happened that after putting in all electrodes, everything looked nice. But I could see DC offset levels slowly rising for all electrodes until eventually they got too high (this happened throughout a couple of minutes). I tried changing all cables (the 2 cables of 32 electrodes each and the CMS/DRL) and I also tried with a different amplifier. Nothing stopped this behavior.
So, after taking the CMS/DRL out and plugging it back in, everything nice again and slowly the offset increasing. Do you have some suggestion as to what might be causing this behavior or what I can do to fix it next time I come across it ?
If there are more details you would like me to provide, please let me know.

Best Regards,
Mihaela

[Coen]

When the offsets of all electrodes drift as if the offsets are locked together, then that's an indication that there is a problem with the CMS/DRL loop. Check the CMS and DRL connections to the skin (not enough gel) and check that there is not a gel bridge between CMS and DRL (too much gel).

Best regards, Coen (BioSemi)