Re: openeeg for GSR?

tnx for that, Stefan.

Regards, B


2013/2/1 Stefan Jung <[email protected]>

> 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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