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AFE4403EVM: Negative values in Ambient channel

Farzad Samie
Prodigy 170 points
Part Number: AFE4403EVM

I'm using the AFE4403EVM along with the TI GUI to get PPG signal from my finger. For the Rx configuration, I use DAC cancellation current of 0.

I see a plausible signal in the LED1 and LED2 channels.

I expect to have small positive values in the Ambient channel that do not change after increasing first stage gain (i.e. Rf)

However, I see negative values AND the values increase after increasing the Rf.

Could you please explain how could that happen? It seems not logical.

Best

  • 0
    TI__Mastermind 19815 points

    Hi,

    Let's take a step back, were you able to follow the user guide to see something similar to Figure 46?

    -----------------------------------------------------------------------------

    After above,

    Would you please provide a picture of your experiment setup and environment?

    Optical experiment is very sensitive to the environment, and any slightly change in angles, offsets, distances, and any optical related components could cause drastically differences.

    What do you mean by "Plausible" signal? could you provide a screenshot or picture as well?

    Thanks