Hi all, today I did some tests on the whole system.
Connecting 100k, 1meg or 10meg to ground produdced too much 50Hz
interference to be reliable, so I have not created any images of
that. It looked like a lot of noise on top of the 50Hz signal though.
50-100 microvolt perhaps... Did I observe the current noise caused by
amplifiers, or something else?
I could not see any 'motorboating' oscillations today, perhaps it was
caused by a ground loop in my previous test setup? I am not using
optical isolation yet, because I am still waiting for parts I have
Anyway, the digital section (12-bit AD converter + microcontroller)
works great, but I'm still wary about the EEG-amplifier.
By the way, I had some problems with the serial port on the new
computer in the lab. The motherboard uses the nforce-chipset from
Nvidia... I could read data for a few seconds, but then it would stop
coming. When I restarted my program, it worked again. I had to resort
to using an RS232-to-USB converter to make it work. I can only assume
it is a bug in their chipset or chipset driver, as it works fine with
my own computer, running the same OS (win2k) ;o)