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ADS1299EEGFE-PDK: Floating baseline for EMG Application

Indrayudd Roy Chowdhury
Prodigy 10 points
Part Number: ADS1299EEGFE-PDK
Other Parts Discussed in Thread: ADS1299

Hi all,

I'm trying to use the ADS1299 FE board for an EMG data acquisition project. It's read through an Arduino Uno. I'll mention the jumper and register configurations with pictures below. 

The resulting signals have a pretty good SNR but with one glaring problem: the EMG baseline floats all over the place, instead of staying fixed around 0. I wonder what setting or jumper configuration I have wrong because I can't seem to mitigate the issue. Help and guidance regarding this would be appreciated. 

Hardware Config:

BIASOUT to BIAS_ELEC

REF_ELEC buffered to SRB1

Register Config:

Signal Output:

Regards,

Indrayudd Roy Chowdhury

  • 0
    TI__Mastermind 19815 points

    Hi,

    May I ask what are the sources of the signal?  Is/Are the source(s) stable/steady/still?

    Is the baseline drifting periodic? can you record the baseline only without signal and do some FFT to figure out whether there is any tone or frequency?

    Could you find&try some steady source of signal and use proper wire/cable to test first? E.g. any ECG, EEG or EMG simulator.

    Thanks

  • 0 in reply to ChienChun Yang
    Prodigy 10 points

    Hello Mr Yang,

    Answering your questions,

    1. The source of the signal is wet electrodes on my forearm as shown in the attached picture. The reference and bias electrodes are connected to my elbow. I do keep my hand and the apparatus as still as possible while recording signals, but it's nothing like a function generator of course.

    2. I'm not sure if it's periodic. Here's the baseline without any triggers. Attaching a clipped version too without the initial transients.

    Here's the FFT of the same signal:

    3. I'll update you on a steady signal source output at the earliest.

  • 0 in reply to Indrayudd Roy Chowdhury
    TI__Mastermind 19815 points

    Hi,

    Warning/disclaimer: "TI never suggests nor recommends to directly use EVM to interact/contact with human body!!"

    Please use some steady/stable signal sources mentioned previously.

    Again, it could be wires/cables and their length and shielding also contribute to drift.

    Skin conditions, hairs also matter/affect.

    You will probably need to design some analog and/or digital filter to reduce the drift.

    Again,

    Warning/disclaimer: "TI never suggests nor recommends to directly use EVM to interact/contact with human body!!"

    Thanks