Simultaneous EEC and ECG: which CMS & DRL to use

[Atlantico]

In our experiment we will be acquiring the ECG using EX1 to EX8 FLAT electrodes, for which I have been using the front-end CMS and DRL connection.

Simultaneously we will be acquiring the EEG using the PIN type electrodes A1 to A32 flat cables electrodes which have their own CMS and DRL.

Which CMS & DRL should I use? Should I use the front-end one for the ECG, puting them in the usual ECG reference locations, and, simultaneously the CMS & DRL located in the usual EEG reference locations?

Cheers

[Coen]

Use only one CMS/DRL, with two CMS/DRL sets connected the Common Mode will not come in range (blue light will remain blinking). So, in your particular case use only the CMS/DRL integrated with the A set (or use an A set without CMS/DRL in combination with the front-panel CMS/DRL).

Best regards, Coen (BioSemi)

[Atlantico]

Thank You, will do that.

[mirek.wyczes]

Is it possible to disable the cap CMS/DRL set by ActiView software and use the auxilary external electrodes? We're also using simultaneous recording, and would like to avoid the situation, when cap CMS/DRL bridge with nearby P electrodes due to gel leak (when using >= 64 EEG electrodes). Thank you.

--
Mirek Wyczesany
Psychophysiology Lab
Jagiellonian University
Kraków, PL

[Coen]

CMS and DRL are configured in hardware, the ActiveTwo system cannot work without these two electrodes, see http://www.biosemi.com/faq/cms&drl.htm . As an alternative for the headcap CMS/DRL electrodes, you can use a flat-type CMS/DRL set connected to the front panel connection on the AD-box (in combination with a 32-chan pin A set without CMS/DRL)

- A short between CMS and one of the measuring electrodes results in a flat line for that particular channel in the raw (unreferenced) signals display, but no effect in the referenced signals (besides an uncertainty of measurement location between the electrode and CMS), CM remains in range (blue light continuously on).

- A short between DRL and one of the measuring electrodes results in high (50/60 Hz) interference for that particular channel in the raw (unreferenced) signals display, but no effect in the referenced signals, CM remains in range (blue light continuously on).

- A short between CMS and DRL results in high (50/60 Hz) interference on all channels in the raw (unreferenced) signals display, with equal amplitude of the interference for all channels (because of a 40 dB reduced Common Mode Rejection Ration), CM remains in range (blue light continuously on).

Best regards, Coen (BioSemi)

[mirek.wyczes]

Thank you for claryfying the issue. When mentioning 'external electrodes' I meant the external DRL/CMS set. Is it possible to use them (and place them let's say on a neck) instead of those from typical 32A+CMS/DRL set? When they are plugged together CMS goes out of range. Is it possible to disable the cap DRL/CMS by software?

[Coen]

You can only use the separate (front-panel) CMS/DRL in combination with an A set without CMS/DRL. Purchase an A set without CMS/DRL, or remove the CMS and DRL from your existing set (split cable as shown in http://www.biosemi.com/faq/split_cables.htm and cut off the 4 wires at the connector)

Best regards, Coen (BioSemi)

[mirek.wyczes]

thank you!

mw.