[Eeglablist] .bdf data converted to microvolts
amani at uh.edu
Thu Oct 23 11:40:01 PDT 2008
I tried what you suggested, but I see the same kind of high values.
But I think that it is not exactly a problem when we look at Bradley
The BioSemi data have such high values, because BioSemi uses some of
its bit depth to record the DC offsets, so the data are oscillating
around (in your case) 9000-1000 uV, instead of around 0. When you
apply a high-pass filter, you are by the very nature of the filter
removing this DC shift (0 Hz), which pulls the data into the
There are a few other caveats to working with your BioSemi data, and
we've had these discussions on this list before, if you look through
2008/10/18 arno delorme <arno at ucsd.edu>
> Dear Abigail,
> are you using a custom program to record BDF files. We are using Alois
> Schlogl function in the BIOSIG toolbox
> to import data so I would first download the latest version of his toolbox
> to see if you still experience the problem when importing the data from the
> command line (sopen and sread functions) and then get back to him if you
> still experience problems.
> Best regards,
> On 11 sept. 08, at 19:28, Abigail Mani wrote:
> EEGLAB users,
>> EEG.data is in uV?.
>> Where does EEGLAB convert the bdf data to uV.
>> How is the conversion done?
>> Sometimes in the eegplot() function under 'Value' i see values in the
>> range of 9000-10000, (even if I use EEG.data matrix, the values are in this
>> after filtering and resampling, i see different values in the range :
>> 150-200. (I was looking at EOG channels recorded with BIOSEMI, sampled at
>> 2048 Hz)
>> Why does this happen?
>> M Abigail
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