Filtering ECG raw data

Dear all, thi message for a comparison with you regarding ECG data filtering. By applying a 5 -50 Hz passband (as seen in the OpenBCI GUI) to ECG raw data saved by Cyton, the corresponding plots do not correspond with those seen during acquisition in the GUI. Maybe I am missing something, just as detial, I am plotting using IGOR and applying a low pass filter at 5Hz e and an high pass filter at 50 Hz. Does anybody experienced something like this? Thank you.

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Giuseppe, hi.

    I am plotting using IGOR and applying a low pass filter at 5Hz e and an high pass filter at 50 Hz. Does anybody experienced something like this?

    You have the filter sense inverted. You want high pass at 5 and low pass at 50. Alternately, and preferable, just use a simple BANDPASS from 5 to 50.

    Regards, William

  • Dear William, thank you ! I solved, just a mistake in setting the filter on Igor....now I was able to plot the ECG correctly, they seem very similar to what I see on the OpenBCI GUI. Lastly, the unit of mesaure on the Y axis, do I need to convert them? or do they represent Vrms dirctly? Best, Giuseppe

  • wjcroftwjcroft Mount Shasta, CA
    edited May 14

    The sample units are microvolts. The GUI shows uVrms as just an indication of average amplitude. Samples have no RMS averaging / smoothing.

    https://en.wikipedia.org/wiki/Root_mean_square

  • abummu1abummu1 Malaysia

    @giuseppetx1
    Pls, can you help me with the code for the filters?
    Thanks in advance

  • Dear, I use a software for plotting and data analysis, IgorPro, it provides a user interface for the filters setting, showing the resulting pass band, the important this is you set the sampling 250 Hz, just to explain see the screenshot in attachment. I know that other software like Origin Pro can provide the same functionalities. Sorry but I am not programming by coding ....
    Giuseppe

    @abummu1 said:
    @giuseppetx1!

    Pls, can you help me with the code for the filters?
    Thanks in advance

  • abummu1abummu1 Malaysia

    @giuseppetx1
    Thanks for the response.

  • abummu1abummu1 Malaysia

    @giuseppetx1
    Pls, how did you insert raw ECG data into the IGOR since it is in a text file? Was it a direct plot or there is a menu for uploading? Thank you for your time

  • Igor can in general read .txt file, but with the openbci raw data I found many problems in importing settings, so the fastest way I am finally using is to organize the columns in a file excel and import that file .xls with Igor, so that the columns are already ordered with the openbci channels, ready to be filtered and plotted.

    @abummu1 said:
    @giuseppetx1
    Pls, how did you insert raw ECG data into the IGOR since it is in a text file? Was it a direct plot or there is a menu for uploading? Thank you for your time

  • abummu1abummu1 Malaysia

    @giuseppetx1
    That's awesome. Thanks for the tips

Sign In or Register to comment.