For patients at risk of developing cardiovascular complications, it is important to monitor their heart signal to ensure proper functioning of their heart and a natural, healthy cardiac cycle. Preferably, this monitoring should be done on a continuous and long-term basis. Both of 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 electrolytic paste makes 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 transmit it to a base station. This could permit the patient to be ambulatory and lead a relatively active life without being confined to a specific region. The project deals specifically with the design of a dry, portable ECG device for this 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 skin and a metal electrode goes on top. The electrode carries an AC bioelectric 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 digitized and logged. The theory behind the device, hardware design and experimental results are presented.
De Armas, Winston, "Design of a Non-intrusive 2-lead ECG System Using the Active Insulated Electrode" (2010). EE 4BI6 Electrical Engineering Biomedical Capstones. Paper 24.