Blood pressure is measured mainly by means of a sphygmomanometer to measure the lateral pressure of the blood vessel wall. The main principle of the sphygmomanometer is the process of pressurizing the air and compressing it to the local artery, stopping the fluctuation of the local artery by applying pressure and thus measuring the blood flow pressure during this period. The most primitive use was the cuff sphygmomanometer. Nowadays, most of them are electronic sphygmomanometers, which can measure the pressure of blood flowing inside the blood vessel. Whether it is a cuff sphygmomanometer or an electronic sphygmomanometer, the pressure of the artery inside the vessel wall is measured by applying pressure to the artery from the outside. The sphygmomanometer needs to be calibrated frequently, and after calibration the accuracy of the cuff sphygmomanometer and the electronic sphygmomanometer is the same. The principle of blood pressure measurement is to monitor the pressure of blood in the blood vessels through external instruments, which is one of the four vital signs of the human body.