What's on the back of the Charge 3?

[kaygeea1]

I just bought a refurbished Charge3, and have successfully set it up.  But no where could I find a description of the objects that are on the backside of the tracker.  I know about the charging pins, and I see an intermittent green light, but what are the other things?

TIA,,

Kaygeea1 

[Odyssey13]

Hi @kaygeea1  you can learn more from the Charge 3 area where there are articles, videos and the user manual. click to go there.

[LZeeW · Accepted solution]

@kaygeea1   What you see is a combination of emitters and sensors.  The green light comes from an LED emitter for measuring heart rate.  There is also a red/infrared light emitter in that same sensor array.  It shines red when you are sleeping.  It will also turn on when you are awake and very still, as you might be getting ready to fall asleep.  It will stay on for sometimes as long as an hour after you wake up.  This part of the emitter shines the light for SpO2.  The two small rectangular objects on each side of the light emitter are the heart rate sensors.  My old Charge HR has an arrangement where there are two HR light emitters and one sensor in the middle.  The rectangular object that is the farthest from the charging pins is the SpO2 sensor.