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Original question:

ADS1299: ADS1299

ADS1299: ECG signal waveform drift problem

Lumina Gui
Genius 3630 points
Part Number: ADS1299

Hi TI Teams,

One of customer report that they have found a ECG signal waveform drift problem when using the PCBA to collect the output data. The details are shown as below:

1) The PCBA board is configured as follows:

-Power supply: analog power +5V, digital power +3.3V;

- Use internal reference voltage and internal clock;

- BIASREF=(AVDD-AVSS)/2;

-Data output rate: 250Hz;

-Gain is 1;

2) Data collection steps:

Stand still for 20 seconds, blink 10 times at 1 second intervals, then close the eyes for 20 seconds, blink 10 times at 1 second intervals, and finally close the eyes for 10 seconds to complete the test.

3) Data waveform as below:

Our customers want to know how this offset can be improved or eliminated? Can you give us some better suggestion for this problem?

Thanks,

Best Regards

  • 0
    TI__Mastermind 19815 points

    Hi,

    Regarding to this " a ECG signal waveform drift" -

    Do they use ADS1299 evaluation kit/board(EVM)? or customer's PCBA?

    And, do they have and ADS1299EVM?

    What was the ECG signal source? human subject or from an ECG simulator?

    Thanks

  • 0 in reply to ChienChun Yang
    Genius 3630 points

    Hi ChienChun,

    The waveform was obtained by measuring EEG signals with ADS1299EVM. The ECG signal is tested using an actual human headband, where the skin is in contact with a silver paste electrode in the headband.

    There is no drift problem when measured by ECG simulator, and the ECG signal is relatively stable.

    Thanks,

    Kind Regards

  • 0 in reply to Lumina Gui
    TI__Mastermind 19815 points

    Hi,

    I will get back to you around Thursday.

    Thanks

  • 0 in reply to ChienChun Yang
    TI__Mastermind 19815 points

    do they use BIAS electrode?
    wet electrodes or dry electrodes? Try wet electrodes first.
    then, ask DC coupled or AC coupled? try both to see which one has less drift issue.
    breath, muscle, motion, skin conditions, wires/cables, electrodes quality, etc could also affect.

  • 0 in reply to ChienChun Yang
    Genius 3630 points

    Hi ChienChun,

    Yes, they have used the BIAS electrode yet, both the dry and semi-dry electrodes (conductive paste) have been tried and have the similar result. The DC coupled was used, and what do you mean by AC coupling and is there any reference design for it?

    Is there a video on how to connect to the human body and a configuration that works better for the ADS1299EVM, is there any reference that you can give to the us?

    Thanks,

    Kind Regards

  • 0 in reply to Lumina Gui
    TI__Mastermind 19815 points

    may consider

    Try wet electrodes first.

    and then

    try different dry electrodes with low impedance and make sure impedance along signal path are very close/match with each other.

    --------------------------------------

    AC couple means put a series capacitor in series between the electrode wire/cable and the ADS1299 input pin along the signal path. 

    We don't have video nor particular reference design for this case in ADS1299.

    We leave the peripheral and the associated configurations to customers as these are really cases by cases and applications by applications dependent.

    Thanks