From: Sajith Goonesekera (sajith_at_magix.com.sg)
Date: 2001-05-28 16:14:57
Hi
At the moment I don't have any EEG probes.
What is the fastest way to get proper probes for testing????
Now I'm drawing analog PCB and soon post it for comments.
And I want to build Digital part before make the PCB.
Are we making RS232 or Sound card method.
I like sound card method. because it's cheap.
and less electronics parts.
sajith
> The RS232EEGanalog03 schematic does not provide any optical
> isolation (isolation would be done on the digital board by optoisolators
> and by using batteries).
>
> So if you power the circuit with a laboratory power supply
> and / or connect an oscilloscope ground to AGND or vref/2
> you will have _no_ protection against isolation failures or PE-failures.
>
> In worst case if you connect yourself via electrode to the amplifier
> this might result in killing yourself.
>
> So be very careful !
>
> A workaround for laboratory testing could be to power the oscilloscope
> with an isolation transformer and to use batteries for the amplifier.
>
> If you want to measure real brainwaves, you need EEG-electrodes
> (and conductive gel) that give sufficiently low impedance (<10kOhms).
>
> Basically you connect a part of the body that is relatively far away from
> where you want to get the signals (e.g. Right leg or right hand ) to
R_LEG.
>
> Then you choose the referecence potential (often right and left earlobes
connected
> together) and connecet it to CH1- and CH2-.
>
> Finally you choose two points of interest from the 10/20 map (e.g. O1, O2)
and
> connect them to CH1+ and CH2+.
>
> To minimize interference you should use shielded cables for Ch1 and ch2
and
> connect the shield single sided to the appropriate shield driver output.
> Make sure, that the shield driver outputs _never_ get in contact with
> ch2+, ch2-, ch1+, ch1- .
>
> Regards
>
> Joerg
>
>
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:30 BST