“At present, due to unscientific eating habits and unhealthy living habits, people are prone to various diseases, and hypertension, as one of them, has seriously threatened the health of modern people. How to detect high blood pressure early has become the primary problem for people to fight against high blood pressure. The current digital sphygmomanometers are also varied, but most of them do not have automatic reporting and self-monitoring functions.
At present, due to unscientific eating habits and unhealthy living habits, people are prone to various diseases, and hypertension, as one of them, has seriously threatened the health of modern people. How to detect high blood pressure early has become the primary problem for people to fight against high blood pressure. The current digital sphygmomanometers are also varied, but most of them do not have automatic reporting and self-monitoring functions. The portable digital sphygmomanometer designed in this paper is a simple-to-operate pressure measuring device, which provides convenience for family health care. Its active reporting and overpressure monitoring and brewing functions provide great convenience, especially for the elderly and blind with poor eyesight.
2. Design block diagram of digital sphygmomanometer system
2.1 Working principle of digital blood pressure monitor
This sphygmomanometer uses the oscillometric method to measure blood pressure. The pressure measurement process is the same as the Korotkoff sound method. The cuff is pressurized to the obstructive artery to block the blood in the blood vessel, and then slowly decompressed. At this time, the fluid in the blood vessel is pulsed due to pressure. Wave method is to use equipment to identify small pressure pulses passed into the cuff from the arm and differentiate them to obtain blood pressure values. There are two main methods for judging blood pressure by oscillometric method: mutation point criterion and fixed ratio calculation method. The design of this system adopts the fixed ratio calculation method, and its judgment method is to first find the maximum amplitude value Amax of the pressure pulse wave. The DC component of blood pressure corresponding to the transient position with an amplitude of 0.8Amax after the maximum value is the diastolic blood pressure, as shown in Figure 1.
2.2 Overall block diagram of the system
The system hardware mainly includes: AT89C51 microcontroller, pressure sensor (BPOl), air pump, filter Amplifier circuit, keyboard module, LCD Display module, voice prompt module and so ON. The specific structural block diagram is shown in Figure 2.
Specifically, through the pressing button on the keyboard module, a signal is sent to the microcontroller to start the air pump to inflate the cuff; the pressure sensor collects the human body and the liquid pulse wave is used as the signal source. After amplifying and filtering circuit, it is transmitted to the single-chip microcomputer for data processing. Finally, blood pressure display and voice reading and overpressure reminder are performed. After completion, the gas in the cuff is quickly discharged through the air release valve switch controlled by the single-chip microcomputer.
3 Software Design
This software adopts the mixed programming of assembly and C language, including subroutines such as inflation, judgment, deflation, data calculation and comparison, display, etc., which can collect useful signals more reliably and separate disturbing physiological signals. The main flow of the system is shown in Figure 3, in which the pressure measurement mode in the mode selection is the default mode.During the measurement, the criteria for abnormal blood pressure are: systolic blood pressure > 140mmHg or systolic blood pressure 90mmHg or diastolic blood pressure map
This paper systematically presents the design principle and scheme of portable digital blood pressure monitor. This system is based on AT89G51 single-chip microcomputer as the control core, plus pressure sensor and peripheral circuits such as amplifying filter circuit, charging and deflating circuit, voice alarm circuit, etc. to design this sphygmomanometer. Has high practical use value.