Versa 2 sensor lights - 4 dropped to 1

[wilderja]

So, when I got my Versa 2 over a year ago, all 4 sensor lights on the back would light up green. Recently, I discovered only one lights up. The heartbeat works. So, my question is: how many SHOULD light up and what are they for?

[AndreaFitbit]

Welcome to the Fitbit Community, @wilderja. Thank you for sharing your Versa 2 sensor lights inquiry. 

When your heart beats, your capillaries expand and contract based on blood volume changes. To determine your heart rate, the optical heart-rate sensor in your Fitbit device flashes its green LEDs many times per second and uses light-sensitive photodiodes to detect these volume changes in the capillaries above your wrist. Then your device calculates how many times your heart beats per minute (bpm).

We use green LEDS because they maximize the signal detected from the capillaries near the surface of the skin. The optical heart-rate sensor also uses infrared light to determine when the device is on your wrist to improve the accuracy of your heart-rate data.

Your watch's HR will work only one green light.

 I hope this information helps. 

[wilderja]

I guess i wasn't clear. The real questions is: what are the other sensor lights for? When I first got this watch all of them flashed. I understand the one, but what are the other sensor lights for?

Thanks.

[AndreaFitbit]

Thanks for getting back to us and for sharing your question @wilderja. 

First Fitbit trackers that registered heart rate needed one than more light to make the HR work. That's why at first all of them flashed. With updates there's only need of one light and the other sensor lights were meant for this at the beginning.

I hope this information helps.