Research Of Noncontact ECG Mesaurement Based On Capacitive Coupling

Cardiovascular disease has become the main threat to people’s physical health. Each year the number of deaths from cardiovascular disease accounted for sixty-three percent of the current chronic disease mortality. Measurement and analysis of the ECG signal can accurately determine the condition of the cardiovascular disease. Early detection, early prevention and early treatment, can greatly reduce the mortality of cardiovascular disease. Non-contact ECG measurement system designed in this paper can measure human ECG signal without directly contact to human body, This system make cardiovascular disease diagnosis and monitoring more convenient and reliable.This non-contact ECG measurement system is consisted of non-contact ECG electrodes, ECG signal conditioning circuit, wireless data transmission module and PC ECG display program. The contactless ECG electrode is designed based on capacitive coupling principle. Through a capacitor consisted of a metal plate with the human body, The contactless ECG electrode can couple ECG signals of human body via the capacitance coupling effect. There are two non-contact ECG electrodes and a piece of the right leg drive electrode on the surface of the close-fitting clothing. The ECG signal acquisited by non-contact ECG electrodes is amplified and filtered by the ECG signal conditioning circuit and will be sampled by the STM32 microcontroller. After digital filtering processing by the STM32 microcontroller the ECG signals will be showed a real-time electrocardiogram on an OLED. The ECG signal will be transported to the PC via a Bluetooth module on the ECG signal conditioning circuit. Upper computer program written by Labview was called ECG display program, ECG display program can filter the ECG signal and can reveal two kinds of electrocardiogram. The ECG display program can clearly show the ECG parameters such as amplitude and time.A series of experiment was made to test the function of this system. Such as non-contact electrical measuring electrode performance contrast experiment, the right leg drive circuit of common-mode interference suppression effect experiment and PC ECG display test. Analysis of experiment shows that this system can satisfy the demand of non-contact detection of ECG signal of the human body.