How does mi band detect heart rate?

1. At present, both the mi band photosensitive plate and the Xiaomi bracelet 2 have the function of measuring heart rate, and the photoelectric heart rate sensor on the back of the rice grain of the bracelet is used to measure and detect the heart rate.

2. The measurement principle is: Photoelectric plethysmography (PPG) to monitor the heart rate. The principle is simple: blood is red, reflecting red light and absorbing green light. Mi band combines green LED light with photosensitive photodiode to detect the blood circulation at the wrist at a specific time, thus obtaining the heart rate information.

3, detection method: just put the bracelet on your wrist to automatically detect.

Knowledge expansion:

1. Photoplethysmography (hereinafter referred to as PPG) is a non-invasive method to detect blood volume changes in living tissues by photoelectric means. When a light beam with a certain wavelength irradiates the skin surface of the fingertip, the light beam will be transmitted to the photoelectric receiver by transmission or reflection. In this process, the light intensity detected by the detector will be weakened due to the absorption attenuation of the skin, muscles and blood at the detection end.

2. Absorption of light by skin, muscles and tissues. It remains unchanged in the whole blood circulation, while the blood volume in the skin pulsates under the action of the heart. When the heart contracts, the peripheral blood volume is the largest, the light absorption is also the largest, and the detected light intensity is the smallest.

3. On the contrary, when the heart is relaxed, the detected light intensity is the largest, so the light intensity received by the light receiver changes in a pulsating manner. By converting the light intensity change signal into an electrical signal, the change of volume pulse blood flow can be obtained. It can be seen that volume pulse blood flow contains many important physiological information of cardiovascular system, such as blood flow.

4. At the same time, volume pulse blood flow mainly exists in arterioles, capillaries and other capillaries in peripheral blood vessels, so volume pulse blood flow also contains rich physiological and pathological information of microcirculation, which is an important information source for us to study the human circulatory system. ?