Lights emmiting from back

gelie

macrumors 6502
Original poster
Mar 7, 2010
469
176
Im pretty sure when the salesperson helped me set up my watch i saw lights emitting from the back of the watch? If so why and how can i replicate this? thx
 

menace3

macrumors 6502a
Aug 13, 2008
552
151
Seattle, WA
Depending on activity, it will light up. If you decide to check your heart rate right now, for example, the lights will light up and check for your heart rate.
 

Armen

macrumors 604
Apr 30, 2013
7,375
2,207
Los Angeles
Im pretty sure when the salesperson helped me set up my watch i saw lights emitting from the back of the watch? If so why and how can i replicate this? thx
swipe up on the watch face. This will take you to Glances. Swipe left/right until you find the heartrate glance. with that on screen the green lights underneath the watch light up.
 

TimUSCA

macrumors 6502a
Mar 17, 2006
698
1,491
Aiken, SC
It turns on occasionally throughout the day to check your resting heart rate. Otherwise, it turns on when you pull up your heart rate Glance or if you have an active workout.
 

CellXor10

macrumors regular
Apr 23, 2015
174
76
Connecticut, USA
Further info on "How Apple Watch Measures Your Heart Rate" from their website:

"The heart rate sensor in Apple Watch uses what is known as photoplethysmography. This technology, while difficult to pronounce, is based on a very simple fact: Blood is red because it reflects red light and absorbs green light. Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment. When your heart beats, the blood flow in your wrist — and the green light absorption — is greater. Between beats, it’s less. By flashing its LED lights hundreds of times per second, Apple Watch can calculate the number of times the heart beats each minute — your heart rate. In addition, the heart rate sensor is designed to compensate for low signal levels by increasing both LED brightness and sampling rate."