Microcontroller-based electronic device MN101EF32D design (1).

<P> Introduction </ P> <P> blood pressure is extremely important health indicators, blood pressure measurement accuracy is directly related to people's health. .Countries to <U> blood pressure </ U> as a compulsory certification of measuring instruments. .<U> General hospital use of mercury sphygmomanometer </ U> Artificial Korotkoff sound method, this method has some inherent drawbacks: First, the speed of deflation has a direct impact on the readings, the international standard deflation rate per second .3 ~ 5mmHg, and different doctors have fast or slow bleed will affect the measurement accuracy; Second, this approach to human vision, hearing, and based primarily on the degree of coordination, difficult to standardize. .Therefore, this design started from the blood pressure detection, the use of Panasonic high-speed, low power MN101EF32D SCM, as the blood pressure measurement, control, data read and write data show that the core of the oscillometric method can be used accurately (oscillation .Law) Measurement of blood pressure. .</ P> <P> works </ P> <P> oscillometric method (oscillation method) is based on the cuff in the decompression process, the pressure changes in oscillatory amplitude envelope to determine the blood pressure. .More consistent view of the current cuff pressure when the maximum oscillatory amplitude, the cuff pressure is the mean arterial pressure. .Artery systolic pressure corresponds to the amplitude envelope of the first turning point, diastolic blood pressure corresponds to the second envelope inflection point. .</ P> <P> hardware design </ P> <P> basic working principle of the system shown in Figure 1. .Pressure sensor output voltage signal of the first through a low pass filter, followed by the op-amp circuit for the signal into the microcontroller input signal, the last of the sampled signal after analog conversion to digital MN101EF32D MCU. .Program data collected after the analysis of digital filtering to calculate the two key indicators of human blood "diastolic" and "systolic blood pressure," immediately after the MCU to external memory data storage, and these important data displayed on the LCD on .. .</ P> <P align=center> </ P> <P> </ P> <P> Shao sensor and its peripheral circuit design </ P> <P> the blood pressure sensor using MPS-3100- .006G piezoresistive pressure sensor is composed of four equivalent resistance benefits-style bridge, the output voltage and input pressure is proportional to the input when the pressure under ideal conditions, the resistance to change with it, but in fact temperature changes .also affect the resistance output. .In addition, because the crystal and circuit design error, coupled with other aspects of packaging process, zero offset is not zero. .External components must be carried out by the individual temperature compensation circuit correction. .The key indicators are as follows: </ P> <P> a, the sensor measurement range: 5.8 ~ 15 PSIG </ P> <P> b, operating temperature range:? 40 ~ 85 ℃ </ P> <P> c, drive .Current: 1.5 ~ 3mA </ P> <P> d, driving voltage: 5 ~ 15V </ P> <P> e, zero drift:? 25 ~ 25mV </ P> <P> f, temperature coefficient of resistance: .0.2% / ℃ because the blood pressure signal from the arm cuff measurement signal vulnerable position, move the arm brought the interference. .According to these specialized features, requires a system with high input impedance, high gain, high common mode rejection ratio, low noise and low drift characteristics. .Shown in Figure 2, the figure, T1 is the MPS-3100-006G piezoresistive pressure sensor. .First, the circuit pressure signal is converted to voltage signal, and then amplifying and filtering. .Figure U1, U2 for the active op amp LM324, its input impedance is high. .Pressure sensor signals amplified, and by adjusting the size of VR1 to change the op amp's closed-loop gain to adjust to meet the A / D input voltage range. .U1 transported back into the road used to measure the pressure in the cuff, the measurement data used for analysis and control MCU cuff inflation and deflation speed. .U2 is also transported back into the road blocking capacitor C11 through the exchange of signal amplification, this circuit measures the body's pulse wave. .Two data acquisition circuit constitutes an important target blood pressure in all calculated parameters. .</ P> <P align=center> </ P> <P> </ P> <P>.