From: Psytrix Yahoo (psytrix_v_at_yahoo.com)
Date: 2001-06-07 02:57:53
Hi, Thanks for answering -
The question which remains is : would be possible that the right leg connection could be more necessary only in
ECG but not so in EEG (considering the legs bifurcation from heart horizontal derivations for ECG and
the "head convergence" at the neck level ) , or
that right leg connection would be replaced for other locations like brow'sor occipital electrodes ( for the same reason ? ) .
Subject: Re: [buildcheapeeg] Re: Right Leg connection for EEG
Hi,
----- Original Message -----
From: Psytrix Yahoo <psytrix_v_at_yahoo.com>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Wednesday, June 06, 2001 2:57 PM
Subject: [buildcheapeeg] Re: Right Leg connection for EEG
...
>Hi, Joerg
> thanks for patience (infinity) with the "starving hobbyist" questions .
> Would you give some references (WWW or texts) about the right leg connection for EEG -
> I found it only for ECG
The purpose of a driven right leg is the same for ECG and EEG:
Reduction of common mode voltage at the amplifier inputs.
Basically the common mode voltage (Vcm) is amplified and inverted and fedback into the right leg
(could be any part of the body that is sufficiently far away from the signal uptaking electrodes)
of the test subject.
This setup forms a servo circuit (closed loop control), that minimizes Vcm.
See chapter: 3.2 "Reduction of the common mode voltage"
at http://www.biosemi.com/publications/artikel3.htm
(IIRR yaniv had discovered this very good series of articles )
Regards,
Joerg
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