Automatic electrode selection in unobtrusive capacitive ECG measurements

Due to the demographic change and increased cost pressure, contactless measurement methods such as capacitive ECG become more and more interesting in research and industry. As these electrodes shall be integrated in objects of daily life to unobtrusively monitor patients (e.g. a chair or a bed), one major problem arises: no medical expert attaches the electrodes and it is a priori not known to which electrodes the patient will have the best contact. Hence, several electrodes are usually integrated and this paper proposes a simple but robust method to automatically select the best coupled electrodes for the deduction of an ECG. It uses the driven right leg (DRL)-electrode to capacitively inject a high frequency voltage into the patient which is then capacitively received and analysed by each electrode. The electrodes with the largest high frequency signal are then used for the deduction of the ECG.