Study On Noncontact Electrocardiogram Measurement System

Nowadays, cardiovascular diseases (CVD) are becoming one of the leading causes responsible for disability and premature death in China. Electrocardiogram (ECG) is a main mean for CVD diagnosis. Long term ECG monitoring and analysis are helpful for preventing and treating CVD at early stage and thus improving the outcome. In this thesis, we designed a noncontact ECG measurement system, which is able to detect ECG effectively while being attached at clothes.The system consists of three parts:the capacitive coupled electrodes, the analog circuits for signal acquisition and the signal processing program. Two capacitive coupled electrodes and one reference electrode are attached on subjects’ clothes. The signal obtained by electrodes is preprocessed by the analog circuits at first, then sampled by a data acquisition control unit and finally processed by signal processing program. The results show that the system has low impact on subjects, avoids skin allergies and electrodes polarization during long term monitoring. The obtained ECG can be used to calculate the parameters such as heart rate or RR interval, which are vital for monitoring.Experiments are designed to investigate the factors affecting the ECG quality, for instance clothes materials, clothes thickness and the gain of Direct-Right-Leg circuits. On the basis of the analysis of test results, the optimal working conditions for the system are accordingly obtained. Meanwhile, in order to improve the comfort of the long term measurement, the feasibility of the application of reduced electrodes in noncontact ECG system is discussed. Consequently, two-electrode ECG acquisition design is proposed.