Please note: Although this question mentions an electronic circuit depicting an EEG, I believe this is purely a bio-electrical question that is appropriate for this site, and should be answered by any battle-weary Biomedical Engineers that have had experience with EEG.
I stumbled across this DIY EEG Instructable, which is interesting and novel, but which has a number of drawbacks (from an EE perspective).
What surprises me most about this circuit is the constant amount of correction/filtering that the author is doing at each step:
- Two 60Hz notch filters one at each "end" of the circuit, to reduce noise at a particular frequency (do we really need two?)
- High pass filter for circumventing galvanic skin response
- Low pass filter for waves > 30Hz
- Yet another high pass filter
To me, it makes sense to digitize the circuit upfront (by running the analog brain waves through an analog-to-digital converter, or ADC).
This leaves me feeling that perhaps there is some intrinsic/inherent value to EEG evaluation of analog (as opposed to digital) waves. So I ask: is there a compelling reason to tune/correct/filter raw analog brainwave/analog signals for EEG, or is it perfectly fine to digitize the waves and then process them?