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Problem of AFE4490 and Reflective pulse oximeter

wang dongming54855
Prodigy 20 points
Other Parts Discussed in Thread: AFE4400, AFE4403

Hi,I'm developing a reflective pulse/oxy device detect heartrate by toe,using AFE4400,I find that someone is very difficult to get the PPG signal，we have the same product using transmissive type，and it works well。The reflective type is too difficult because the signal is weak and easy operational when adjust the amplifier ，either adjust the LEDCNTRL or TIAGAIN，the result is not very good,it puzzled me a long time.So i want to know someone‘s advice who has faced with much the same problem.How can i improve the signal，to amplify it to fit the arithmetic？Shall I select other reflective pulse/oxy sensor or adjust the register of AFE44xx？thanks very much！

1. good（RED、IRed 、weight）

2.Bad signal（RED、HR）

  • 0
    TI__Mastermind 49786 points

    Hello Wang,

    PPG signals are also highly sensitive to measurement site (finger, wrist, toes etc.), motion artifacts, ambient light and mechanical setup and this is more pronounced for reflective sensors than for transmissive sensors (finger clip).

    Yes we have also noticed similar behavior with reflective sensor.

    Did you try the AFE TIA, 2nd stage gain settings to increase the DC and AC amplitude?

    You may also try increasing the LED current.

    Which reflective sensor are you using in your application?

     

    Regards

    Praveen.

  • 0 in reply to Praveen Aroul
    Prodigy 20 points

    Hi,Praveen,Thanks a lot for your reply！I have tried increase the LED current and 2nd stage gain.The reflective sensor i used is DLED-660/905-CSL-2 and PIN-4.0CSL by OSI optoelectronics(a red and the other ired led)，The ambient light I have tried onece,but almost the same.I will try later.The sensor of AFE4403 EVM board is also reflective ,from GUI the pulse waveform looks very good,except the digital filter on PC GUI，so i think this can be reserved by AFE.Unfortunately we have no ideal about this，can you please give me some advice?

    Thank you very much！