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AFE4403EVM: How to process the result of the SPO2 sensor and the meaning of GUI output, such as LED1, LED1 ambient, LED2/LED3, LED2/LED3 ambient

Hao Ren
Prodigy 10 points
Part Number: AFE4403EVM

Hi, I bought a AFE4403EVM, and I am able to follow the manual to install the GUI, driver and also obtain some preliminary results. I have some questions regarding the results, please help me, thanks.

When I look at the result from the GUI, it has the LED1, LED1 ambient, LED2/LED3, LED2/LED3 ambient

1. May I ask how do I obtain the SPO2 from these graphs? 

I looked at some documents, R=ACrms of Red/DCred / (ACrms of IR/DCIR), and SPO2=110-(25*R)

2.Also, I am not sure what do the LED1, LED1 ambient, LED2/LED3, LED2/LED3 ambient stands for? Is the LED1 the red LED, LED2 infrared? LED3 Green LED? Does the LED2/LED3 is the voltage of LED2/LED3?

3. I suppose all the results of voltage are from the photodiode output?

4. Why does this Evaluation board has a green LED? According to the manual, the third green LED isenabled with TX3 mode in the TX Stage tab during the measurement.

Thanks in advance!

  • 0
    TI__Genius 12575 points
    Hi Hao,

    Few answers.
    1) Typically SpO2 is calculated based on some empirical formula. The one mentioned above is one of them. Its the user who decides the formula/algorithm to convert the raw data into SpO2.
    2) You can refer to section 9 of the user guide to find about the LED association with the color for the given sensor board.
    3) Photodiode gives current output, which is converted into voltage by the Trans-Impedance Amplifier and then converted into digital codes by ADC.
    4) Some user use Green LED for heart rate measurement.

    Regards,
    Prabin