Fitbit Versa Red/Green LED (HR/Spo2 sensor)

A short video showing the HR sensor on the Fitbit Versa flashing between green and red. The purple light at the beginning and end of the video is an infra-red (only visible when viewed with a camera, can't be seen with the naked eye) light.

[davidblack]

I have the charge 3 device and I was wondering if you could tell me what’s the red sensor on the back of device....it normally comes on when you go to bed plus with the spo2 sensor now Fitbit support says my device can pick up the levels but on the app it don’t clue how to access it