[FieldTrip] Amplifier for EGI-data in fieldtrip???

Thu Sep 13 09:21:00 CEST 2012

Yes, it works fine now-thank you!!!

@Matt: Do you know a calibration-function for existing raw-files?

Best,

Daria

2012/9/10 Joseph Dien <jdien07 at mac.com>

> Hey Daria,
>    glad you were able to get it worked out!  Thank Matt for his reminder
> (below) about the calibration option.
>
> Cheers!
>
> Joe
>
>
> Hi Joe,
>
>
> I didn’t know that there is a function like this.
>
> The most of my colleagues use the RAW.-files they get from the
> file-exporter without problems.
>
> Not even NetStation-support could give me an answer.
>
> So I thought, it must be a problem between NetStation and fieldtrip.
>
> Because of your tip I opened an original datafile and tried to save a copy
> of the file.
>
> Doing so NetStation offers a possibility to ‘convert to microvolts’ and
> create a .ses –datafile.
>
> The .raw-files I get this way have microvolt as unit.
>
> I compared the signals I get this way with the signals I get by using the
> formula (5000 mircovolts / (2^16 bits) I send you. They are almost the
> same-that’s great!!!
>
> It seems to work now.
>
> Thank you very much!!! You were a great help!!!
>
>
> Cheers,
>
> Daria
>
> On Sep 6, 2012, at 9:07 PM, Joseph Dien <jdien07 at mac.com> wrote:
>
> I don't recall ever seeing this problem with EGIS files, which is one of
> the reasons I prefer using this file format despite EGI's preference for
> newer Simple Binary format, but it's an unpredictable bug so I can't say it
> can't happen. I also can't say which versions of NetStation it happens
> with. It may have been fixed.  I'm still trying to test out MFF so can't
> say anything about it. I had problems with the FieldTrip code for reading
> segmented MFF files (which is what I'm interested in).  I also had trouble
> with writing them out from NetStation so I don't have a valid segmented
> test file and I'm still waiting for EGI to make one available so I can work
> them out. The simple binary file format (this is the original name for the
> EGI .raw file format and I prefer to use it over ".raw" as the BESA .raw
> file format is actually the .egis file format so it can get confusing)
> doesn't actually have separate calibration information for the channels
> (unlike EGIS), just one single gain value and no zeros values.  So
> basically the simple binary format makes the assumption that calibration
> corrections have already been performed prior to generating the file.  My
> understanding is that this is indeed what the "calibrate data" option is
> doing, but you'd have to confirm with EGI.
>
> Joe
>
>
>
> --------------------------------------------------------------------------------
>
> On Sep 6, 2012, at 1:01 PM, Matt Mollison <matt.mollison at gmail.com> wrote:
>
> Joe,
>
> A few related questions:
>
> Does using the "calibrate data" option when exporting to raw (simple
> binary) correct for gain? Or is there a different solution/recommendation?
> Does exporting to MFF (Net Station 4.5.x only) or EGIS have this issue? I
> tend to use EGIS (faster to read than raw) and have no recollection of
> seeing unusually large voltages.
>
> Thanks,
> Matt
>
> --
> Univ. of Colorado at Boulder
> Dept. of Psychology and Neuroscience
> matthew.mollison at colorado.edu
> http://psych.colorado.edu/~mollison/
>
> On Wed, Sep 5, 2012 at 7:17 PM, Joseph Dien <jdien07 at mac.com> wrote:
>
>> The Simple Binary (.raw) files don't get corrected for gain when imported
>> (I helped write them).  I've experienced occasional unpredictable bugs with
>> NetStation export routines where the files are generated with amplitudes
>> many times too large, even with text format files.  It's a bit
>> disconcerting to say the least.  I could take a look at your files if you'd
>> like confirmation.
>>
>> Joe
>>
>> On Sep 4, 2012, at 4:00 PM, Ingrid Nieuwenhuis <inieuwenhuis at BERKELEY.EDU>
>> wrote:
>>
>>  Hi Daria,
>>
>> Also, did you try looking at your raw data (so before the ERPs are made)
>> in FieldTrip and in Net Station? So open your .raw data in NetStation. You
>> can just look at a random participant's data, and check if the scale is the
>> same. I'm pretty sure no amplification takes place when reading in the data
>> into FieldTrip, this check can confirm that. Hope this helps, and let us
>> know what you find.
>>
>> Cheers,
>> Ingrid
>>
>>
>> On 9/3/2012 1:35 PM, Robert Oostenveld wrote:
>>
>> Hi Daria,
>>
>>  There might indeed be an incompatibility in the gain  value applied to
>> the data.
>>
>>  If you are able to export the data using the EGI software in another
>> format (e.g. EDF), you could read them both into FieldTrip and compare the
>> timecourse aplitudes to check whether they are different. In case they are,
>> I suggest to involve EGI support. They are aware of the FieldTrip reading
>> functions and will know much more about the internals of their various file
>> formats.
>>
>>  best regards
>> Robert
>>
>>
>>
>>
>>  On 3 Sep 2012, at 17:22, Daria Laptinskaya wrote:
>>
>> Dear Fieldtrippers,
>>
>> I analysed EGI-data (.raw-files, NetStation 4.3.) with the fieldtrip
>> toolbox.
>> The ERPs look perfect.
>> The 'only' problem is, that my signals look to strong.
>> It looks like if I get amplitutes (average) until 70 µV.
>> I think it must be an intern amplifier for the signals.
>>
>> Does anyone know this problem with EGI-data?
>>
>> Or does anyone know, where I can see the amplifier?
>>
>>
>>
>> Greetings,
>> Daria _______________________________________________
>> fieldtrip mailing list
>> fieldtrip at donders.ru.nl
>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>>
>>
>>
>> _______________________________________________
>> fieldtrip mailing listfieldtrip at donders.ru.nlhttp://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>>
>> --
>> Ingrid Nieuwenhuis PhD
>> Postdoctoral Fellow
>> Sleep and Neuroimaging Laboratory
>> Department of Psychology
>> University of California, Berkeley
>> California 94720-1650
>> Tolman Hall, room 5305
>>
>>  _______________________________________________
>> fieldtrip mailing list
>> fieldtrip at donders.ru.nl
>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>>
>>
>>
>> --------------------------------------------------------------------------------
>>
>> Joseph Dien,
>> Senior Research Scientist
>> University of Maryland
>>
>> E-mail: jdien07 at mac.com
>> Phone: 301-226-8848
>> Fax: 301-226-8811
>> http://joedien.com//
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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>>
>
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>
>
>
> --------------------------------------------------------------------------------
>
> Joseph Dien,
> Senior Research Scientist
> University of Maryland
>
> E-mail: jdien07 at mac.com
> Phone: 301-226-8848
> Fax: 301-226-8811
> http://joedien.com//
>
>
>
>
>
>
>
>
>
>
>
>
>
> --------------------------------------------------------------------------------
>
> Joseph Dien,
> Senior Research Scientist
> University of Maryland
>
> E-mail: jdien07 at mac.com
> Phone: 301-226-8848
> Fax: 301-226-8811
> http://joedien.com//
>
>
>
>
>
>
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