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Motion Artifact Reduction with AFE4490

Brian Leung
Intellectual 325 points

Other Parts Discussed in Thread: AFE4490

Hi all,

I just bought an EVM of AFE4490 and trying to get IR, Red signals from the GUI tool.

It seems to me that signals are highly susceptible to motion artifacts and just wonder if there are any methods of reduction the motion artifact?

In the meantime, I was puzzled why the ADC resolution is that high? (22-bit).

Regards,

Brian

  • 0
    TI__Guru 50036 points

    Hello Brian,

    Yes PPG signals are highly sensitive to motion artifacts and this is more pronounced for reflective sensors than for transmissive sensors (finger clip) and minimizing the motion artifact out of PPG signals has been the holy grail that every player in this business has been trying to address. Information from additional sensors such as accelerometers along with sophisticated algorithms can be used to reduce the motion artifact out of PPG signals. For methodologies please refer to academic papers that address this issue.

    Regarding the ADC resolution, the pulse oximeter signal from the photodiode to the AFE comprises a pulsatile (AC) component riding on top of a DC component. The DC component represents the signal due to light transmission through veins and tissue, where the blood volume is invariant with time. It also includes a component of ambient light that gets into the photodiode. The pulsatile signal that is a measure of the pulsating arterial blood flow and oxygenation can be very small as compared to the DC component. This necessitates a signal chain with a very high dynamic range - hence the 22-bit ADC.

    Best Regards

    Praveen Aroul.