Re: openeeg for GSR?

TEZ

You can't use an EEG amp for GSR/SCL measurements.
You need to apply a test voltage/current and a EEG amp does not do so.

I am going to attach two documents "as is" - meaning they are for info,
I am not willing to go into technical discussions as to their merrits or
implementation.  I simply havn't got the time to do so.

The first circuit is a derivitive of what is used in the "lighstone" from
the Wild Divine gaming device (the lighstone can do SCL and HRV).

Almost everyone does DC skin conductance level measurement.  I believe that
AC measurement has much better performance due to polarization effects of
most type of electrodes.  I thus designed an AC circuit based on the
original concept.  It's simply a cmos switch that is toggled at a 50% duty
cycle at anything between 20 to 100Hz.  The cmos switch just inverts the
two SCL measuring leads.  Just ignore all the other crap at top and right
side of the scan.
R20 & R 21 where included to convert to simple DC measurement, by simply
dropping the TS5A cmos switch and fitting 0ohm resistors.
Diodes D2 & D3 are for ESD protection.
R19 is a calibration resitor for when nothing is plugged into J2, this
resitor disconnects when a jack is plugged in.

This work was done for a lightstone plug & play, WD software compatible
replacement about 5 years ago... so I can't remember all the details now.

The DC sensing, or the slightly more complicated AC sensing circuit could
be build and easily integrated into modEEG on one of it's spare analog
input channels.  Or you could interface it to an Ardunio or other
micro-based development board.  Just remember that modEEG has a FSD input
of 4.095V.  I suggest adding a simple resistive divider to lower the 5V
output of the AD623 to the required 4.095V for modEEG's AVR, or you could
handle the scaling in software.

Regards
Stefan

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