the wave of the data in afe4400 sensor

Hello Wei,

The first image below is the time series plot of the changes in light absorption also referred to as the photoplethysmogram (PPG). During each cardiac cycle, the heart is pumping blood to the periphery. The pressure pulse is detected by shining light with the LED (red and IR) onto the skin and then measuring the amount of light transmitted to a photodiode. Each cardiac cycle appears as a peak as seen in the image. Since it is the same cardiac cycle when Red and IR LEDs are alternately turned on, you will notice the same shape for both Red and IR phases. 

The image below is the absorption coefficient of light at different wavelengths especially the red and IR wavelengths. The blue curve refers to the absorption coefficient at 0% SpO2 and the red curve refers to the absorption coefficient at 100% SpO2. This image provides insight into the wavelength dependent properties of blood. It shows that deoxygenated haemoglobin (HHb) absorbs more red light  than IR light and oxygenated haemoglobin (O₂Hb) absorbs more IR light than red light.

 Hi,Praveen Aroul:

thank you , I think i was wrong in the understand of the theory of measuring the oxygen.