| In recent years , with the improvement of people's living standard and the change of the meal structure ,the incidence of disease and death rate taking arteriosclerosis as representative cardiovascular disease are higher and higher , World Health Organization classifies it as No.1 killer endangering the human health seriously in the 21st century. So, how to prevent and cure the disease, become a subject which need urgently to be solved in all over the world.In the initial stage of cardiovascular disease, though patients do not have obvious symptoms, but a series of cardiovascular blood flow parameters,such as blood pressure, blood flow, blood vessel obstruction,blood vessel elasticity and blood viscidity ,etc. Have already changed, at the same time, the pulse wave form has changed, too. Through comparing the normal pulse wave with non-normal pulse wave, we can probably diagnose the cardiovascular disease in the initial stage.Pulsology is an important component of Chinese medicine ,mine while ,it is one of the important means in clinical diagnosis of the disease either, although many Chinese pulsology reasoning has a reasonable side, after all, it is just a subjective sensations and is lack of objective and scientific. Therefore, to inherit and pioneering Chinese Pulsology, realizing the scientific of Pulsology is very important. The appearance of computer makes digital signal processing technology into a powerful signal processing tools, in order to make digital signal processing technology used in pulse research, scholars at home and abroad have done a lot of work. Although some progress has been made in pulse signal processing with computer, however, there is a large distance with the objective of diagnosis means.The pulse test system described in this paper can meet the demands of both doctors and patients, it has the advantages in high accuracy, low price, and is convenient to carry and use, and the hardware and software is designed novelty. This paper is divided into four chapters. In the first chapter, it briefed the importance of pulse detection and the features of various pulse acquisition systems.In the second chapter, it details the design of the hardware circuit of the instrument, including the design of PPG pulse sensor, the design of amplify filter circuit, the outer circuit of MCU, in order to have a better understanding to the hole system, it also makes a brief introduction to USB bus and USB communication protocols in this chapter.PPG pulse sensorsWe use infrared transmitter-receiver pair of pipe as sensors to complete electro-optical, electro-optical conversion. SIR333 is selected for infrared emitting diode and BPW83 is selected for infrared receiver diode, here we use reflective design.Large filter circuitWe choose AD620 as amplifiers, it has low drift, high input impedance, and high common-mode rejection ratio and so on. In the part of signal filtering, we design the active second-order low-pass filter circuit.MCU and its external circuitC8051F320 is a mixed-signal integrated system on a chip, and has CIP51 Micro-controller core, which is compatible to MCS51.It has 10 bit ADC, USB controller, internal clocks, and other functional device. Its external circuit design includes programmable amplifier circuit ,level upgrade circuit and power supply circuit.In the third chapter details the design of software to the system, including the firmware program, USB drivers, Application procedures and the baseline drift correction program.Firmware ProgramFirmware Program is compiled with C language, including system initialization module, main cycle module and interruption subroutine modules.Date acquisition programThe Date managing program is compiled with Visual Basic 6.0, through the visual interface; it realizes the function of pulse testing, parameter testing and program-controlled amplification.Software filtering programPulse waveform is a relatively low-frequency signal, its major spectral energy distributes from 0.3Hz to 20Hz. In the process of pulse measurement, it is easy to introduce low-frequent interference and make the baseline of pulse waveform drift .Here we use the method of wavelet transform to curb baseline drift, the program is compiled by C language.The fourth chapter presents the experiment results and makes analysis to the data; it is conformed that the pulse waveform can reflect characteristics of human pulse accurately. |
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