Study On Acquisition System Of ECG Signal Based On Virtual Instrument

The electrocardiogram (ECG) technique has been one of indispensable methods for diagnosis, observation and research of cardiology, because of its good characteristics. For example, easily operation, noninvasive, etc. In decades of years, the clinical applied area of ECG has become wider and wider. Some techniques use it for signing the time and phase. For example, phonocardiogram, ultrasonic cardiogram, cardio-radionuclide angiography and noninvasive cardiac detection, etc. In the 863 project "Technique and Device for Detecting the Function and Status of Cardiovascular System" the ECG signal is also used to mark phonocardiogram signal and pulse wave signal and evaluate the function and status of cardiovascular system. Virtual instrument is one type of new high-tech production with the develop of computer technology and modern medical metrical technology, which represents the new develop trend of medical instrument, and is fit for the research of medical and biomedical engineering.A suit of acquisition and study system of ECG signal based on virtual instrument has been designed in this paper for the request of ECG detection. The main job of this paper is as follow.(1) The amplifier and filter circuit of the ECG signal. The main frequency range of ECG is 0.05～100Hz, and the amplitude is 0～4mV. Because of the mixed other biomedical signal and 50Hz electromagnetic interference the ECG signal has more noise and is harder to measure. The ECG amplifier designed in this paper has high precision, high stability, high CMRR, low noise and strong ability of anti-jamming, which can detect ECG signal without distortion.(2) The security and ECG lead. Because the ECG electrodes contact directly with the skin, we design a isolation scheme in order to assure the safety of the measured person. The system is in the float ground situation through the dual protection of power isolation and signal isolation. Besides, we measure both ECG signal and other signals in the same time. So, we optimize the lead selection for comfort and facility. (3) The acquisition system based on virtual instrument. We use LabVIEW which is a kind of graphical programming language to design the acquisition system and prepare for the analysis of ECG. The virtual instrument which is designed by LabVIEW can be away from the develop environment and the user can see the operate panel conformed with the practical one. At the same time, LabVIEW can easily help the designer to found a measure system and instrument panel without complex programme.(4) The analysis of the ECG signal. We remove the wander of the baseline and detect R wave base on the theory of wavelet transform. The result of the experiment is very good.(5) Debug. Debug the system and obtain the required ECG signal.