From: Waldemar Neto (wpneto_at_o...)
Date: 2001-05-22 04:24:53
Most of professional equipment usually has an electrode tester , which we can use for test or include in our
cheapEeg "Aparatus" :
the measures of resistance of each electrode shall be less than 3 kOhms (from ground in monopolar derivation ) - preferably less than 2 kOhms .
In a few cases where the signal is very weak it mays be necessary less than1 kOhm - the ideal - ( like "brain silence" by tumors or CET, extremely fat bald skin, anencephalia and other )
Do you think that would be interesting to include a little level ( Ohmmeter ) with LED activated threshold for that electrode levels ?
----- Original Message -----
From: peterson_at_d...
To: buildcheapeeg_at_yahoogroups.com
Sent: Monday, May 21, 2001 7:29 PM
Subject: [buildcheapeeg] Re: electrodes
--- In buildcheapeeg_at_yahoogroups.com, jiva_at_humboldt1.com wrote:
>
> > > ...
> > > > 2) i wonder if the choice of electrodes might influence
> > > > the issue?
> > >
> > > Different electrode types might have different impedances,
> because. R and C parts of the impedance will vary depending
on
> electrode area, material and used electrolyte / conductive gel.
>
> > Sometimes it's hard to get the same impedance out of the same
> > electrode on two different scalps, or even on 2 different spots
on
> > the same scalp.
>
> Would any of the list members who work with electrodes care to
> choose which to use for this project?
I think that this electrode issue is going to turn out to be less
critical than everybody thinks. I've heard of people mixing tin and
silver electrodes (10 mm disk kind) in the same montage, and people
commonly change from all-tin to all-silver or gold with the same
equipment. The trick is to get the same impedance at all the
electrodes in the montage. I think that just about any kind of
electrode you pick will work. There is probably a lot more impedance
variation between the bald, exposed skin on top of my head at Cz and
the skin at my haired-over mastoid process behind my ear than there
is between any two different electrode types you are likely to see in
common use. Just choose something and go with it.
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:30 BST