The method of measuring heart rate with a 37-degree bracelet is still light sensing. The body of the 37-degree bracelet has a light sensing module. This module, like Moto 360, uses green light to illuminate the blood vessels of the arm (preferably the left hand), and it is calculated by the change of the absorption degree of red blood cells in the subcutaneous capillaries. When the heart pumps new blood into capillaries, the brightness (red depth) changes slightly. This regularly changing interval is monitored by sensors, and then the heart rate can be obtained through a series of algorithms.
In addition, the 37-degree bracelet also has an optical module for measuring blood pressure, which uses a white light source. Its principle is to measure the blood flow rate, capture the subtle changes of blood vessels and skin color when blood flows, and calculate with the help of image information processing technology and image blood pressure algorithm, which takes about 30 seconds.