Recently, telemonitoring of vital signs has gained a lot of research interest. Especially for electrocardiogram (ECG), which is among the most frequently measured vital sign. However, the integration of classical ECG Holter in wearables is problematic since shielded cables and gel electrodes are required to get ECG signals of highest quality. We have recently introduced a novel sensing architecture based on active electrodes (so-called cooperative sensors) that significantly reduces the cabling complexity of the monitoring device. After briefly recalling the principle of cooperative sensors this paper details how they address rejection of common-mode voltage induced by electromagnetic disturbances. The proposed approach uses an auto-identification technique based on a continuous-time calibration of the sensor system and a digital control loop. To demonstrate the reliability of the proposed approach, a 12-lead ECG monitoring system was implemented with the new common-mode rejection method. Measurements on four healthy volunteers showed that the signal quality obtained with the cooperative-sensor system (using dry electrodes) is equivalent to the one measured with a gold standard medical device (using gel electrodes) in exercise stress tests.
at - Automatisierungstechnik, vol. 66 (12), pp. 1002-1013