# How to test an EEG?

Apologies out of the gate here as I'm a CS person with not a huge amount of experience in electronics, so this might be a pretty basic question. I've built basic EEGs before, basically electrodes together with a series of active filters.

My approach in the past has always been to play with my filters until I don't see a peak at 60Hz, and I don't see huge swings when someone moves their eyes. Once that's done there's usually some kind of wave that gets spit out, but I've never really been convinced that I was seeing a real signal, and not just picking up on some other random noise, which is extremely likely.

I'm now a bit older and more foolish and I wanted to take a more intentional stab at this, but I was wondering if there's any reasonable way of testing this. My naive approach was going to be attempting to generate a signal in the nV realm as input, then trying to re-create it after processing. There are two main reasons why I think this doesn't make sense:

1. Electrodes/Skin conduct introduce noise that I can't model this way
2. I'm very unclear on exactly why an EEG works. It feels very strange to me that you'd get actual signal by strapping electrodes to your head

So how exactly do I test an EEG, and have confidence that an EEG I create is working?

• – Roger Rowland Mar 1 '17 at 6:35