INVERSION OF PPG SIGNAL

[PChiericoUPV]

Platform your question concerns:

• Android
• iOS
• Other
• Platform is not relevant for this question

Device:

• Polar OH1
• Polar Verity Sense
• Polar H10
• Polar H9
• Other
• Device is not relevant for this question

Description:
I would like to understand if the PPG signal is inverted, as the systolic phase seems to align with the literature only when I invert the signal on the Y-axis.

Regarding the three PPG channels, does Ch0 represent the photodiode of two opposite LEDs?

Additionally, concerning ambient light, is there an Automatic Light Control (ALC) in the device? Does anyone have advice for effectively using raw ambient light data? For me, averaging the three channels and subtracting the ambient light is not robust enough. Is there a method o subtract, perhaps using the median or an alternative average of the ambient light?