muV units and ADC units

[thorn101]

Hi,
A while ago I bought a Neurosky MindWave and recently I started writing my own parser so I'm not tied to one platform (I'm hooking the MindWave up to a BSD server ).
I finished a great deal of the code, but now I'm not sure what type of values I'm supposed to get.

I'm getting the raw ADC values, which I'm converting to voltage per this post http://support.neurosky.com/kb/technolo ... on-mindset

The following sample measurements are the result

Code: Select all

0.000002
0.000002
0.000005
0.000009
0.000009
0.000007
0.000007
0.000011
0.000011
0.000002
-0.000003
-0.000002
-0.000001

I gather these are micro volts, so when I multiply them by a million I get

Code: Select all

37.133789
23.950195
-12.744141
14.062500
33.398438
14.721680
-38.891602
-15.820312
8.349609
-40.869141
-68.115234
-50.976562
-8.129883

Is this correct, in the sense that raw voltage measurements should look like these values.
Thanks in advance for the time taken to read my post.

[mellinger]

For human EEG, amplitudes are expected to be roughly between 30 and 100muV. For muscular artifacts, values will be larger (up to 500muV).
So I guess your values are correct. For more information about EEG, see
http://www.bci2000.org/wiki/index.php/U ... ment_Setup
Towards the bottom of the page, typical wave forms of EEG signals and artifacts are provided.

Regards,
Juergen

[thorn101]

Thank you very much for your response.
Just one quick question, do you know of any other active general fora regarding BCI and EEG.
Neurosky's forum seems non-functional (and doesn't look like that will change any time soon), and I feel awkward posting
general questions here, since it's not about BCI2000.

Again, thanks a million.
Alex

[mellinger]

I'm not aware of forums that deal with EEG and BCI in a generic manner. I guess the BCI2000 forum comes close -- there are a number of sub-forums dedicated to general questions about BCIs, but these are not used much. Also, general EEG questions are welcome as long as these are of interest to BCI2000 users as well. However, EEG is a quite complex topic, and you cannot expect advice or information beyond what is relevant within the scope of BCI2000.

Regards,
Juergen