How do smartwatches measure heart rate and other vital signs, and what sensors are used?

Question

I can understand the heart rate part since watches are worn on the wrist, where our pulse can be determined, though I’m not quite sure, but what about the other vital signs? how? 

In: Technology

Answer 1

Smartwatches use optical heart rate sensors for pulse detection, usually with green LEDs and photodiodes to measure blood flow. For other vitals, they have motion sensors like accelerometers and gyroscopes, barometers for altitude and respiration, and sometimes even EKG sensors for detailed heart activity. They’re almost mini medical devices now.