Amplification of BCI2000 System EEG Signals

[sgupta]

I have the dataset IIa from BCI Competition 2003. I would like to know that what will I have todo to get the absolute values of EEG signals in microVolts. I have read that the amplification used for this dataset was 20000. Does that mean simply dividing the signal values by 20000 would give me absolute values ?

Please help....

[gschalk]

Hi,

The numbers are in units of A/D units. The conversion factor to micro Volts is 0.008.

I hope this helps,
Gerv

[faisal1]

hi gerv,

i have a dataset collected from the EEG machine having Fs=200hz, and amplication of 10000 . How i could the absolute value of EEG data.

Is their any const value to multiply , and if so How could we calculate it????

Regards
Faisal

[gschalk]

Faisal,

This completely depends on the bit resolution of your A/D converter and the input range of your A/D card/EEG system. The easiest thing is if you acquire a signal with a known amplitude, and then see how large it is. This will determine the conversion factor.

Gerv