Huawei bracelet 4 on the table also measured the heart rate?

The capillaries of human skin will expand and contract with the fluctuation of pulse. This subtle fluctuation can be accurately detected by pumping the PPG optical signal into the skin (refer to Bill-Lambert Law for physical principles). In the static state, the fluctuation of this optical signal is basically consistent with the fluctuation of human heart rate, so wearable devices can accurately calculate the heart rate value through this fluctuation. .

Why do you need to measure your heart rate physically? -Because the essence of PPG optical heart rate measurement is to calculate the heart rate through the fluctuation frequency of optical signals, and the fluctuation of light is everywhere in real life, such as fluorescent lamps with alternating 50Hz. Although it is imperceptible to human eyes, the optical heart rate sensor can accurately detect these changes. These fluctuations of ambient light are the same as the changes of light signals caused by skin vascular fluctuations, which is also the reason why heart rate can be measured physically, but this does not affect the accuracy of heart rate measurement when the human body wears wearable devices.