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ADS1292R: ADS1292R ECG waveform related issues.

hasmukh prajapati
Prodigy 20 points
Part Number: ADS1292R

Greetings!!!

We are using ADS1292R chipset for measuring HR(heart rate) and RR(respiration rate) in our application. We are using 3 leads connection. We referred ADS1292R evaluation kit schematic for developing our design.

We are getting proper waveforms while testing in AC(air-conditioned) LAB. 

When we are testing outside AC LAB, ECG waveforms changes as below.

Scenario : 1

The base line of ECG waveform goes around 1677216 while walking and ECG peak goes to 0. 

Scenario : 2

 

The graph between two peaks looks not so smooth.ECG graph should changes smoothly but it gives certain peaks between two ECG peaks as shown in above figure. This problem goes away after restarting the device.

I suspect such behaviour is because of Sweat around the electrodes(probes) on the body. 

Please guide to rectify the issue.

Thanks.

  • 0
    TI__Guru 66346 points
    Hello Hasmukh,

    Welcome to our forum and thank you for your post!

    The second image looks like the ADC output is saturating to full-scale. This means that the voltage at the input of the ADC channel exceeds the reference voltage. Such a large voltage could be caused by an offset voltage that develops between two electrodes with different skin-electrode contact impedance. The voltage must remain less than +/-VREF x PGA at the input of the ADS1292R channel to avoid saturation.

    On a side note, remember that the ADS1292R outputs codes in binary two's complement format. The largest positive code will be 8,388,607 (0x7FFFFF) and the largest negative code will be 8,388,608 (0x800000).

    The noise you see along the ECG baseline could be introduced by a number of factors, including power line noise, motion artifacts, or other active circuitry. ECG systems typically require additional post-processing algorithms to remove such noise sources. Unfortunately, our team is not able to help with such algorithm development.

    Regards