How to invert the ppg signal

[ajmalazees]

The ppg signal obtained through this code is an inverted graph nah? therefore i want to invert the ppg signal t get the proper output for my project. Also my project is to calculate hemoglobin concentration, how can i modify the above code to calculate hemoglobin concentration.

I want to get the ppg signal as below

[adelalfusail]

Exactly I entered to ask this question the PPG wave is inverted put I thank the problem is coming from probe the red and infrared PD is not connected correctly so I am now try to open my probe and check it than I will tell you what is the result

[niv22]

I have the same concern. Is there a reason why the PPG signal is inverted?

[joicetm]

Hi niv22,

The signal from afe4490 comes by default as "inverted from other ppg publications".
It is mentioned in the datasheet on page 82. There is no option given in the afe4490 to invert the signal directly from the chip but you can use some software techniques to invert the signal if it is required.

[niv22]

@joicetm, that was helpful. Thank you.