Lot of noise plus shifting in Electric guru and OpenVibe

Started by pgicquel, July 07, 2015, 11:33:10 am

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pgicquel

Dear Olimex users and team,

I just received my EEG-SMT and have a lot of trouble make it
giving consistent data.

The first picture is with Electric guru, 4 active electrode, 1 passive on the right ear

Notice that I could not use the scale 256 to 752 proposed on the quick start manual so I
used -100-150
The first graph might be OK even if the variation are really tiny, but the second graph is clearly
only noise.

Then I used openVibe with no better results, I used the configuration recommended in quickstart :

Here on both channel there seems to be only noise.


I made a last test, disconnecting the Electrode and acquiring signal with openvibe that confused me
more :

Here all the electrodes (including passive) or disconnected, and there seems to be lot of random noise from nowhere.

I must precise that I tryied differents solution associated with noise found on the forum with no success. I don't think my laptop is the problem because I have a Olimex EKG-EMG wich works just fine.
I would appreciate any help, thank you very much in advance

pgicquel

It seems to get a lot better by these three step :
-changing the USB port I was using
-disconnecting laptop from current (on battery to avoid 50Hz interference)
-changing in electric guru the machine parameter to BrainMaster, then back to the previous one.


I now have acceptable EEG in elec guru where I can distinguish eye blink for instance. OpenVibe seems as well more happy with the charger disconnected and the other usb port (it is a port that has more current I think, there is a small charge icon next to it).

I suggest Olimex to highlight the fact that computer should be on battery because I think it is a common mistake.

Best