Why would they put 6mA when you are suppose to send 2mA?<p>9v/6mA is 1500Ohms. If they added a 3k resistor in series with their setup, they would've up the total resistance to 4500Ohms, resulting in 9v/4500Ohms = 2mA of current.
With two components you can build a variable constant current source very quickly: <a href="http://users.telenet.be/davshomepage/current-source.htm" rel="nofollow">http://users.telenet.be/davshomepage/current-source.htm</a>
yikes, be careful!<p>Hey, I'm curious how you plan to limit current issues through the electrode contact quality. I know when putting on EEG electrodes you can test the impedance, would something like that be needed here?