Abstract: Under the impetus of the actual needs of modern social life, with the support of electronic sensing technology, electronic sphygmomanometers have been developed and gradually expanded, and the scope of application has been continuously expanded. Compared with traditional sphygmomanometers, electronic sphygmomanometers have rapid response and small stimulation. Advantages such as good compatibility, but at the same time there are disadvantages of accuracy and repeatability. Therefore, the application in modern medical and health activities has certain limitations. In view of the practical problems existing in the application of electronic sphygmomanometer, this paper proposes to use MPXV53GC6U high-performance silicon pressure sensor to meet the actual situation of the noise compensation algorithm, to compensate for the difference in results caused by noise during measurement, in order to achieve Improve the accuracy and stability of the electronic sphygmomanometer as a whole.
Blood pressure is one of the important physiological parameters of the human body. The accuracy of its measurement results will directly affect the judgment of human health, and it can play an important role in preventing diseases and treating diseases as soon as possible. This paper takes the oscillometric method as the blueprint and improves the software design and hardware structure of the current electronic sphygmomanometer. The main content of the improvement involves the measurement signal processing technology and the intelligent control technology of the measurement process, in order to minimize the measurement process. The probability of noise interference and measurement data distortion occurring, and its impact on the results. To improve the accuracy and stability of the operation of the electronic sphygmomanometer and to improve its automation and intelligence level.
1 system hardware design
This design uses Motorola's MPXV53GC6U silicon pressure sensor and Atmel's AT89S51 series of single-chip microcomputers to form an electronic sphygmomanometer. The system includes MCU, sensor, LCD liquid crystal display, operation panel, charge and discharge control circuit, air pump and air valve, buzzer, memory, power supply and so on.
MCU is the core center of the whole electronic sphygmomanometer. Its own running quality and operating efficiency will directly affect the operation quality and efficiency of the whole electronic sphygmomanometer. Therefore, it is very important to select the MCU. According to the system design requirements, this article selects Atmel Company. The 16-bit AT89S51 series MCU has a certain automatic control capability. In addition to the system monitoring and data processing capabilities, it can also reset the parameters of the system components according to the overall operation of the system. The initiative configuration and initiative capabilities allow it to have certain autonomy and intelligence capabilities.
The sensor circuit is the blood pressure measurement point of the electronic sphygmomanometer. It should have the characteristics of excellent linear condition, low noise and fast response. According to the requirements of this standard, this paper selects the MPXV53GC6U silicon pressure sensor produced by Motorola. The sensor not only satisfies the design requirements of the electronic sphygmomanometer for the sensor circuit, but also automatically compensates for the temperature difference in the case of constant current power supply. In the actual voltage measurement activity, the sensor's blood pressure measurement signal is filtered by the filter, and then amplified by the amplifier. Through the comprehensive processing of the sensor circuit signal, the calculated systolic pressure (SP), diastolic pressure (DP), The mean pressure (MP) results are displayed on the integrated display of the electronic sphygmomanometer.
The main problem of the current electronic sphygmomanometer is the measurement of the noise problem of the sensor. The wide amplitude and high frequency noise make the measurement signal of the electric blood pressure sensor submerged in the background noise, and the processor cannot effectively process it, thereby affecting the electronic blood pressure. The accuracy and stability of the measurement results. Therefore, it is necessary to add a filter circuit in the electronic sphygmomanometer circuit. The filter is located behind the system sensor. During the measurement of the sensor signal transmission, the clutter signal existing in the signal is filtered to reduce the average noise level of the signal. Improve the quality of measurement signals.
The charge and discharge circuit is the main action circuit in the system, and it is an important auxiliary device for the system sensor measurement function. From the perspective of system structure, the valve is deflated. However, in the specific measurement activities, there are still practical problems of rapid inflation, rapid deflation, and precise control of gas volume. In order to meet the requirements of the above-mentioned charging and discharging circuit in the system design activities, the pressure value control system is selected to perform the charging and discharging circuit. Specific operations. Specifically, the operation flow is as follows. First, press the START button to start the inflation process of the blood pressure measuring sleeve. When the pressure in the sleeve reaches the set value, the charging and discharging circuit will control the solenoid valve to enter the deflation program, and its operating state. It will turn to a uniform deflation until the pressure detection system finds that the air pressure in the sleeve is reduced to 30mmHg. At this time, it can be considered that the blood pressure measurement work has been completed, and the charge and discharge circuit will command the fully open solenoid valve to guide the full speed deflation. The pressure in the sleeve is reduced to zero.
Liquid crystal display is the most obvious difference between electronic sphygmomanometer and traditional sphygmomanometer. It is also the advantage of electronic sphygmomanometer. Usually, in order to ensure the portability of electronic sphygmomanometer and effectively control the cost, a small liquid crystal display is selected. This article selects the small liquid crystal system LMS0192A, which has an external size of 79×42mm and has a 44-pin and 160×64 dot matrix display. The outstanding feature of this display is the internal application of large-scale integrated circuits and controllers. Its own data display function is fully compatible with the single-chip microcomputer. It can display 8 serial data at the same time, and it has a certain data buffer function. Store and realistically detect data for a certain period of time. The liquid crystal display module is also equipped with a power drive circuit, which can help the liquid crystal display optimize the power resource configuration to achieve the best measurement display with minimum power consumption.
Sixth, the design of the power module, the system power supply of this experiment is powered by two 1.5V batteries, and the AT89S51 chip is boosted to 3.5V to directly supply power to the system.
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