Performance Evaluation of Dry and Wet Electrodes for a Wearable Single Arm Electrocardiograph System

Electrocardiographic (ECG) signals are crucial in healthcare applications, particularly for out-of-hospital monitoring of vital signs. Wearable technologies are widely used for this purpose, but they often generate ECG signals of low quality or interfere with the user's daily activities. In addition, low-impedance contact electrodes are commonly used to record bioelectrical signals, which require skin preparation and the application of conductive gels. Those make electrode placement complicated, time-consuming and uncomfortable for the patient. Therefore, the adoption of wearable dry sensors is preferable especially for long-term ECG signal recording. However, the impedance of dry electrodes is significantly higher than that of conventional electrodes, resulting in a lower amplitude of ECG signals and requiring high-impedance amplifiers for signal acquisition. In this work, we employed a prototype consisting in an armband with embedded electrodes and evaluated its performance with both wet electrodes, characterized by better conductivity, and dry electrodes, more suitable for devices designed for long-term wear. We conducted exploratory tests on different electrode positions in the upper arm to study how the distance from the heart and the distance between electrodes affects the intensity and attenuation of the ECG signal recorded with the prototype board, aiming to optimize its use with dry electrodes. The designed device offers comfort and autonomy and could be a promising solution for the automatic recognition of cardiac arrhythmias.