| Oxygen is an essential element for the metabolism of human tissues and cells. Its main carrier is the hemoglobin in the body. Hemoglobin includes oxyhemoglobin (HbO2) and reduced hemoglobin (Hb), those radio are called saturation, which is an important indicator of the oxygen carrying capacity of blood. This has proven to be an integral part of clinical care in a real-life information base. The human body hypoxia will cause damage of the trunk, as well as more serious brain damage and death. So for the nursing process real-time acquisition oxygen saturation coefficient is very necessary.Oxygen saturation comprehensive instrument is a continuous real-time monitoring data, the patient harm noninvasive measurement more convenient instrument to detect human arterial oxygen saturation and pulse rate. But the design of the system is still not a small defect in the signal processing, and thus the accuracy of its measurement data, repeatability and stability of the system there are many other aspects can be developed and perfected.The system is designed for oximetry parameters of oxygen required accuracy, anti-interference ability and low power design requirements. From the design of the system using low-power NXP’s LPC1678as the main chip, eventually designed as a non-invasive blood oxygen saturation detector. Primary signal amplification using a controllable gain amplifier circuit, according to the magnitude of BOLD signal can be collected in real time and then compare the magnitude of feedback regulation of the master drive probe signal. Signal amplification system designed partly based on the differential op amp amplifier circuit to improve the signal to noise ratio, increasing the signal common mode rejection ratio. For the measurement of ambient light interference, designed a set of AC and DC separation circuit, which can effectively separate the red and infrared light hardware timing signals, eliminating the interference of ambient light, improve the working capacity of the system. Signal for the DC component of red and infrared light extraction using a voltage-controlled voltage source second-order low-pass filter circuit. Late signal using a frequency notch filter circuit of50Hz mains frequency interference, and achieved good results. Signal backend using differential threshold and median filtering algorithm based on oversampling the bottom of the pulse wave in the system pretreatment, extraction of more accurate data, the signal usefulness of the system is greatly improved. Finally, will the data in real-time oxygen packaged in accordance with BCI protocol, sent out in the form of Ethernet. Available on the remote PC, convenient interactive software can display real-time waveform pulse wave and R-value is calculated based on the introduction of the system equations, can be regarded as the last of different people of different values of oxygen saturation and pulse rate values.The design of the final measured value of five different student’s oximetry and pulse rate value by more than the system in terms of performance and data accuracy fully meet the requirements of medical care. Circuit simulation and actual test results demonstrate the overall design feasibility and reliability of the program, which is promoting the development of the medical industry will play a great role in promoting the product level. |
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