1 Working principle of the system
Blood pressure refers to the lateral pressure of the blood in the blood vessel against the blood vessel wall per unit area, that is, the pressure. A normal heart is a powerful muscle organ. It shrinks rhythmically day and night, allowing blood to flow through the circulating organs. When blood flows in a blood vessel, whether the heart contracts or relaxes, it exerts a certain pressure on the blood vessel wall. There are two types of blood pressure. One is systolic pressure, which means that when the ventricle contracts, the aortic pressure rises sharply and reaches the highest value in the middle of the systole. The other is diastolic blood pressure, which refers to the decrease in aortic pressure during ventricular diastole. The lowest value of arterial blood pressure at the end of diastole is called diastolic blood pressure, also known as "low pressure".
The multifunctional electronic sphygmomanometer uses the oscillometric method for measurement. Its principle is to measure the vibration of the blood vessel wall when blood flows. During the cuff deflation process, as long as the pressure in the cuff is the same as the blood vessel pressure, the vibration is the most Strong. Its advantages are: easy to use, can be operated by one person alone, the measured value is easy to record, the volume is light and easy to carry.
2 Hardware design
2.1 Overall system structure
The overall structure block diagram of the multifunctional electronic sphygmomanometer system is shown in Figure 1. It mainly includes 6 major modules including LPC3250 main control module, power supply and reset module, detection module, LCD touch screen module, WiFi module, voice module and USB module.
2.2 Main control LPC3250
The main control adopts NXP's newly-integrated highly integrated LPC3250 microprocessor, which has the characteristics of high performance, high integration and low power consumption, which is very suitable for the design requirements of this program. It uses a 90 nm process and a powerful ARM926EJ-S core, clocked at up to 208 MHz, with a full range of standard peripherals. These include a 24-bit LCD controller with a dedicated DMA controller, which can support STN and TFT panels; three-channel 10-bit 400 kHz A / D converter with touch screen interface; internally integrated up to 11 PWM channels; USB OTG interface, capable Connect the host and device at full speed; an external memory controller that supports DDR and SDR SDRAM, SRAM, FLASH and static devices. It fully meets the needs of this design. Only a few chips can be added to realize the system functions, and the entire system can be reduced in size, power consumption, stability and cost.
2.3 Pressure sensor XFGN-6025KPGSR
The design uses a new generation of pressure sensor XFGN-6025KPGSR produced by Fujikura of Japan. Its weight is only 0.35 g. It is mainly used for portable electronic sphygmomanometers. It uses precision thick-film ceramic chips and nylon plastic packages. It contains amplification, temperature compensation and pre-conditioning Correct the offset voltage and range, thereby improving the accuracy and stability of the measurement, and eliminating the amplifier circuit. It directly converts blood pressure into an electrical signal of 0 ~ 4.5 V, and the corresponding blood pressure value is 0 ~ 25 kPa, that is, 0 ~ 187.5 mmHg, which is very compatible with the design requirements of the sphygmomanometer.
2.4 Filter MAX267
The measured analog signal is also filtered and then A / D converted. The filtering is used to filter out the DC component of the signal, the high-frequency noise and power frequency interference of the power supply and the friction between the skin and the cuff. This design uses Maxim's MAX267, which is a simpler of Maxim's many switched capacitor filter (SCF) chips. It contains two second-order SCFs and one op amp that have been fixed into a band-pass type and use the same Q parameters and frequency conversion ratio. By choosing appropriate feedback resistors and Q parameters, Butterworth or Chebyshev filters with different ripple rates can be formed. This greatly reduces the peripheral circuits, and the use of flexible, performance is far superior to the use of integrated op amp filter circuit, very suitable for this design.
Tower Fan Heater With FAN by electric Power, 1500 or 2000 Watts of Powerful Heat, Design well, Great for Home, Office, Tip-Over and Overheat Protection, With Remote Control, Timer, Black, Digital tower Fan Heater is equiped with fireframe, looks like a fireplace. Fortlessly create a warmer and ambient atmosphere in any room or office with this ultra-sleek and space-saving tower heater, offering up to 2000W of powerful heating to warm up your home in time.
Welcome to our factorye, we focus on quality heating.
thanks
Tower Fan Heater
Oscillating Tower Fan,Ultra Air Performance Tower Fan,Tower Fan With Remote,Tower Heater And Fan
Fenry manufacturing Co., Ltd , https://www.cnfenry.com