Sphygmomanometers, also known as blood pressure monitors, are mainly available as auscultatory sphygmomanometers and oscillometric sphygmomanometers. The auscultation method is divided into manual auscultation method and automatic auscultation method. Mercury sphygmomanometer, spring gauge sphygmomanometer is the early manual auscultation method sphygmomanometer. Manual auscultation method has digital sphygmomanometer, light column sphygmomanometer, light display sphygmomanometer, liquid crystal sphygmomanometer. The difficulty factor of the automation of the auscultation method is larger, and the automation of the Koch auscultation method will be the main direction of the development of the sphygmomanometer. Oscillometric method is also called oscillometric method, simply put, is to obtain the oscillatory wave generated in the process of deflation, through a certain algorithm to convert the blood pressure value. The vast majority of electronic sphygmomanometers are designed using the oscillometric principle.