Research On Non - Contact ECG Signal Acquisition System Based On Fabric Electrode

Cardiovascular disease has become the main cause of human disabilities and premature death, and electrocardiogram (ECG) is a major means of diagnosing cardiovascular disease. Long-term monitoring and analysis of ECG to achieve the early warning and treatment of cardiovascular diseases have an important function in reducing morbidity and mortality. Traditional ECG signal acquisition systems still primarily use wet electrodes that consist of a metal plate on an adhesive sheet with the skin-electrode interface conducted through a glue paste. Consequently, the preparation for each detection is complicated and is unsuitable for high-density, long-term, wearable ECG acquisition systems.Conventional clinical ECG systems, such as the widely used Holter systems, employ several Ag-AgCl electrodes, which are attached to specific parts of the body, including the chest, arms, or legs. Although this type of system has good signal quality, it is inconvenient to use and may cause skin irritations or allergic reactions because of the toxicity of the glue. More importantly, the quality of the acquired signals worsens because the glue dehydrates in long-term measurements. Therefore, a wet-electrode ECG acquisition system is unsuitable for long-term ECG detection. In this study, we present an ECG signal acquisition system based on capacitively coupled textile electrodes. The system consists of capacitively coupled textile electrodes, signal acquisition module, signal processing module, power-supply module and upper computer program. We designed electrodes that have a composite and textile structure. A kind of conductive textile with stainless steel wire creates these electrodes. We wove the conductive textile with Three-Dimensional Woven Method. According to circuit models of the skin-electrode interface, the influence of the area of coupling electrode, the distance between the human skin and the electrode and the material of the clothing on the coupling capacitance is analyzed. By means of a series capacitor in the coupling capacitor, the influence of the distance between the electrode and the human skin is obviously reduced. Both circuit models of the skin-electrode interface and amplifier for the capacitively coupled textile electrode were established, and the output signal-to-noise ratio (SNR) of the front-end circuit was proposed. In the experimental part, the accuracy of signal acquisition was tested by using Fluke-ProSim 2 Vital Signs Simulator. And the effectiveness of the capacitive coupling electrode was tested respectively via 0.25mm,0.51mm and 0.89mm of cotton clothing. The results show that the signal acquisition system studied in this paper signal acquisition is accurate and reliable. Using the PCB plate capacitive coupling electrode, the QRS wave group and T wave can be effectively collected via 0.89mm thick cotton clothing. Using capacitively coupled textile electrodes, the R wave and T wave can be effectively collected via 0.51mm thick cotton clothing.In this study, we present an ECG signal acquisition system based on capacitively coupled textile electrodes. We used conductive textile instead of a rigid metal plate as the capacitive electrode. The conductive textile improved the comfort of the patients during detection. The acquired ECG signals could reflect heartbeat characteristics, and the system is applicable in clinics and in daily life.