DESIGN AND DEVELOPMENT OF CAPACITIVE ELECTRODES FOR WEARABLE ECG SENSOR

The technique of Capacitive Electrocardiography (cECG) is very promising in a flexible manner. The measurement and record of the electrical activity of the heart is an essential diagnostic tool. A wide range of heart conditions can be detected when interpreting the recorded ECG signal. The commonly used ECG machine used for patient diagnosis and supervision at present is expensive and stationary. On the present research work a small sized ECG embedded system capable to make the patient more mobile without losing the reliability of the ECG sensor. 

For patient at risk of developing cardiovascular complications, it is important to monitor their heart signal to ensure proper of their heart natural healthy cardiac cycle preferably; this monitoring should be done on a continuous and long term basis. These objectives can be achieved using the electrocardiogram while the traditional 12 lead ECG is currently used in hospital and clinical settings, the number of wires and the need for an electrolyte paste make the setup very inconvenient, invasive and unsuitable for long term use. The goal is to develop a clinical diagnostic system to take physiological signals from the patient and monitor on the digital oscilloscope continuously. This could permit the patient to be ambulatory and lead a relatively active life without being confined to a specific reason. 

The project deals specifically with the design of a dry portable ECG system. The exclusion of wet electrodes without direct patient contact is achieved using the insulated dry electrode. The fundamental concept involved is the principle of capacitive coupling and the use of an impedance transformation circuit at the head stage. An insulating dielectric layer is placed in direct contact with the patient’s T-shirt and a metal electrode goes on top. The electrode carries an AC bio-electric signal through the capacitance of the coupling and this can then be conditioned in the analog domain. An analog ECG signal can be extracted, which can be analyzed by the signal conditioning system (or ECG amplifier). 

Keywords: ECG electrocardiograph, capacitive coupling, dry electrode, non- contact, capacitive electrode.