With the improvement of people's material level, people's health requirements have not only stayed at the level of treating diseases, but also proposed new topics for disease prevention and health care. As the second biggest killer of human health, cardiovascular disease has caused widespread concern in the medical community. ECG detection technology is a necessary technology for heart disease diagnosis and heart health care. Under the trend of miniaturization, familyization, and network development, it is inevitable that a simpler, lower-cost ECG testing device is needed. A monitor is a device or system that measures and controls a patient's physiological parameters and can be compared to known setpoints to alert if there is an excess. The monitor is different from the monitoring diagnostic instrument. It must continuously monitor the patient's physiological parameters for 24 hours, detect the trend of change, point out the critical situation, and provide the doctor with emergency treatment and treatment basis to minimize complications and achieve relief and eliminate the disease. the goal of. In addition to measuring and monitoring physiological parameters, the monitor also includes monitoring and handling medications and conditions before and after surgery.
The traditional lead system uses a common three-electrode method. The right upper chest electrode and the left lower abdominal electrode are electrocardiographic sampling electrodes, and the right lower abdominal electrode is a right leg driving electrode. This connection method is effective and practical, and is convenient for portable use. The portable monitor analysis and processing system can be divided into two parts, one is a pocket monitor carried on the subject, and the other is an electrocardiogram processing diagnostic system composed of a microcomputer system. The examinee records the dynamic ECG signal of a certain period of time by the monitor, and transmits the data to the hospital's electrocardiogram processing and diagnosis system through GPRS communication. The ECG signal is a rather complex weak signal emitted by the human heart. In order to obtain an ECG signal with less noise, the collected ECG signal needs to be noise-reduced.
Features of this design:(1) At present, there are various methods for noise reduction of ECG signals. Here, the noise is separated from the signal mainly from the aspect of filtering. The filtering adopts high-pass and low-pass two-stage filtering, and the filtering circuit is obviously simulated by Workbench.
(2) Unlike the conventional dual T-type 50 Hz notch filter, the design circuit introduces an amplifier to form a positive feedback to reduce the stop band width.
(3) This article is convenient for human life, and designed a lead electrode drop detection circuit to prevent the moving input electrode from falling off.
1 Characteristics of ECG signals and overall system structureElectrocardiogram (ECG) signal automatic analysis and diagnosis is one of the research hotspots in the field of signal processing. Its real implementation will effectively promote the development of medical undertakings and improve people's health. It will also be modern signal processing theory and technology and labor. A major breakthrough in the application of intelligence and other fields in the medical field. The research and analysis of the automatic analysis and diagnosis system of the electrocardiogram (graph) signal is extensive, and the basic theories and key technologies involved are numerous, which is a huge subject with multiple disciplines. So far, there are still many defects and deficiencies in the existing automatic analysis methods of ECG signals. There are still many areas for improvement and innovation in theoretical research and practical application. In response to this situation, the paper focuses on the key technologies of "electrocardiographic signal preprocessing", "electrocardiogram waveform detection and localization", "electrocardiographic feature extraction and selection" and "automatic classification and recognition of ECG signals". .
The ECG signal is taken from the skin surface by the skin electrode and is a low frequency, weak bipolar signal. It is submerged in many strong disturbances and noise. These disturbances mainly include in vivo interference signals such as myoelectric signals and respiratory wave signals, and the effects of external electromagnetic field interference signals mainly based on 50 Hz power frequency interference and noise between the electrodes and the skin interface. The signal source impedance is about 100 kΩ, the signal is 10μV~5 mV, the typical value is 1 mV, and the surrounding electromagnetic interference (especially 50 Hz power frequency interference) is relatively large, requiring the amplifier circuit to have high gain, high input impedance and High common mode rejection ratio; in order to keep the signal stable, the input offset voltage and bias current are small, and the temperature drift is small; in order to facilitate carrying, it also requires small volume, low power supply voltage, and low power consumption.
For accurate measurement of ECG signals, an amplifier with excellent performance must be designed. The core and key of the amplifier is the design of the pre-stage. The entire pre-stage circuit is composed of a preamplifier circuit, a trap circuit and a filter circuit. After the ECG signal obtained from the body surface is input through the lead, the ECG signal is amplified by the preamplifier formed by the operational amplifier, and the filter filters out the high frequency interference, and then further suppresses the power supply interference through a 50 Hz notch. The A/D conversion is then entered by level shifting to obtain a digitized ECG signal.
2 circuit structure description, sensing, amplification and filtering of ECG signals 2.1 Circuit structure description and simulationThe entire monitor is composed of a preamplifier circuit, a trap circuit and a filter circuit. The medical sensor obtains the ECG signal of the body surface and filters out the interference of other frequency bands, and then transmits it to the computer for data analysis after amplification conditioning and A/D conversion. In terms of portability, the electrode drop detection circuit is designed to get rid of the cable ç¾ç»Š, so that the user can carry it with him. The hardware circuit can be simulated by Workbench software, and the filter function can be designed by Matlab and Filterlab software. After the filtering method adopts 50 Hz notch, it is subjected to high-low-pass two-stage filtering, and the amplifier is introduced to form positive feedback to reduce the stopband width.
2.2 ECG input electrodeEar Plugs,Bluetooth Earplugs,High Fidelity Ear Plugs,Noise Reducing Ear Plugs
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