What does the red light on back of Sense mean?

[JimS2022]

On back of my Sense normally 2 green lights 

but sometimes one of those light turns red 

what does that mean???

Moderator Edit: Clarified subject

[JohnnyRow]

I think red is for SpO2 sensor.

[JimS2022]

Thanks for the info

[JimS2022]

Is there a more in-depth answer 

Can this be explained in layman’s terms?

[JohnnyRow · Accepted solution]

Here's a fairly non-technical article article about it from The Verge:

https://www.theverge.com/23031829/how-to-measure-spo2-smartwatch

I think roughly red and infrared light gets transmitted into wrist, and depending on how much oxygen in blood, different amount of the different wavelengths get reflected back to the sensors on watch.  Fingertip sensors are generally more accurate as the light passes through the finger and sensors are on the other side.

[JimS2022]

Thanks
That’s a little easier for me to understand

Sent from my iPhone