Difference in PPG waveform observed in Eval board and traditional PPG waveform

Traditional PPG waveform is as mentioned below.

Image result for PPG waveform

But the PPG wave  form output i am seeing in ADPD105 is as mentioned below.

I am not understanding why i am observing this kind of output.

Can you please explain me the Reason behind this?.



  • +1
    •  Analog Employees 
    on Nov 11, 2017 1:57 AM

    Hello Lokesh,

    This is a good question. Basically, the waveform that you showed as a comparison to the output of the ADPD105 is a transform of what's being measured by our device. Our device measures intensity, and as the blood volume in the arteries increases following the contraction during the systole phase so does the absorption of the light being shined into the tissue. Since there is more absorption, the PD will receive less reflected light and the output of the ADPD105 will decrease. During the diastole phase while there is less blood in the arteries there will be less absorption and therefore more reflected light to the PD. So the output of the ADPD105 is just an inversion of the PPG plot that you find in most medical texts and papers.