[Bitalino] Negative values in EMG, EDA, and ECG data

Hi. I am a ph.D. student and am currently using Bitalino (r)evolution board to collect EMG, ECG, and EDA data from participants in a VR HMD experiment. The data is being collected simultaneously using a lab streaming recorder and saved in xdf format.

After completing a pilot test and converting the data to CSV for inspection, I noticed that some participants' EMG, EDA, and ECG data were being recorded as negative decimals. I am curious about the possible reasons for this phenomenon and would appreciate any information you can provide.

The attached image shows a portion of the data where the values are negative.

Additional Information:
I am using the latest version of the Bitalino software and firmware.
The Bitalino board is properly connected to the participants.

Thank you for your time and attention to this matter.


  • wjcroftwjcroft Mount Shasta, CA

    Hi Kim,

    This Forum is devoted to OpenBCI users. So very unlikely you will find Bitalino users here.

    I just tried looking around for Bitalino forums / discussion boards. Not seeing any thing. I suggest submitting a ticket on their website,


    Bitalino is made by Plux.

    With OpenBCI devices, biosignals such as EEG, EMG, and ECG, can have both plus and minus samples, because that is what the ADC device returns as sample values.


  • godotkimgodotkim South Korea

    Dear. William,

    I have already searched Bitalino forum and sent an inquiry to Bitalino but couldn't get any response. I am sorry to ask an unappropriate question on this forum. But your kind answer helped me a lot.

    Thank you so much. Have a nice day!

  • wjcroftwjcroft Mount Shasta, CA

    Wikipedia ADC paragraph below

    For example, an ADC with a resolution of 8 bits can encode an analog input to one in 256 different levels (28 = 256). The values can represent the ranges from 0 to 255 (i.e. as unsigned integers) or from −128 to 127 (i.e. as signed integer), depending on the application.

    In the case of OpenBCI Cyton, the samples are signed 24 bit numbers.

    Found this Bitalino doc, see Figure 6 on page 11. Samples are shown to range from -1 mV to +1 mV.


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