The electrocardiogram (ECG) is one of the primary sources of information for assessing cardiovascular function. Conventional ECG systems are not suitable for continuous, long-term monitoring. Contactless measurement of ECG using capacitive sensors is emerging as an attractive alternative. One of the disadvantages of a contactless system is that the signal quality is poor as far as the clinical acceptance of the system is concerned. The contactless ECG signal typically contains a relatively large amount of dc, due to electrode offset or artifacts, which would drive the front end of the high-gain amplifier into saturation. Hence, what is required is a circuit that would effectively block dc while coupling the differential ac signal. A circuit developed for conventional ECG systems has been made use of, for this purpose. This paper describes the simulation and analysis of a contactless ECG monitoring system, using capacitive electrodes, with an ac-coupled front end for effective dc decoupling. The performance of the circuit is studied for different material and thicknesses of clothing.
K. R. Sandra, Anusha, A. S., Dr. Madhu Mohan N., and George, B., “Simulation study of a contactless, capacitive ECG system”, in TENCON 2014 - 2014 IEEE Region 10 Conference, 2014.