Is the raw data saved to the .csv file already referenced to SRB channel?

fraposofraposo Portugal

I'm not sure whether the "raw" data that is written to the .csv file is already referenced to the SRB channel (which is linked to the earlobe electrode) or if I need to apply some reference method to it...

Thanks in advance,


  • wjcroftwjcroft Mount Shasta, CA
    Yes, the default reference is SRB2. This is not a 'channel' per se, but a bus which acts as the other electrode for all the channel pins. The SRB2 electrode can be placed anywhere you desire, not just at the earlobe.

  • fraposofraposo Portugal
    What is the referencing operation that is applied? That is, how are the values written to the .csv file computed in terms of the values measured by both electrodes (a channel and SRB2)?
  • wjcroftwjcroft Mount Shasta, CA
    EEG amplifiers are DIFFERENTIAL, measuring the microvolts between plus and minus electrodes. When you use SRB2, all the IN*P (IN1P, IN2P, etc.) pins are bussed together and appear on the SRB2 pin. Which is typically connected to one or both ear lobes. The IN*N (IN1N, IN2N, etc.) pins then connect to your head 10-20 sites.
  • fraposofraposo Portugal
    I still do not understand. Let me give you an example: I have 1 electrode on the front of my head (FCz) and I have SRB2 connected to my earlobe and BIAS to the other earlobe. How is the value of FCz written in the .csv file computed? FCz - SRB2? FCz - BIAS?
  • wjcroftwjcroft Mount Shasta, CA
    FCz - SRB2. And if you used Cz for example, Cz - SRB2. Etc.

    Bias is a 'ground' connection and is not used for the differential voltage computation.

    If you want more technical details you can view the TI ADS1299 chip data sheet, Technical Docs tab,

  • fraposofraposo Portugal
    Got it. Thank you!
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