Light sensors are used by fitness trackers to determine a person’s heart rate. These are just a couple of examples in addition to others such as sensors that shine light through the skin to help reveal the amount of blood flowing in your body to determine how many times your heart beats per minute.

• The PPG technology is used by the light sensors. PPG is one of the non-intrusive methods for measuring clinical data.
• They utilize green light since red blood absorbs it pretty well. This allows accurate reading from the optical sensor on the amount of blood flowing through, as well as heart-beat counts.
• Each of these trackers has aLEDthat sends a green beam towards the skin in your wrist. At the rear of the tracker there is an optical sensor that senses the reflected light.
• The accuracy in wearable devices is about 20% when it comes to heart rate measurements.