Impedance Measurement System for Determination of Capacitive Electrode Coupling

Capacitive electrodes have been studied as an alternative to gel electrodes, as they allow measurement of biopotentials without conductive contact with the patient. However, because the skin interface is not as precisely defined as with gel electrodes, this could lead to signal deformation and misdiagnoses. Thus, measurement of a capacitive coupling of the electrodes may allow to draw conclusions about the applicability of such systems. In addition, combining capacitive biosignal sensing with an impedance measurement unit may enable bioimpedance measurements, from which additional information on the hydration status can be extracted. A prototype system is introduced which measures impedance over capacitive electrodes in parallel with biopotential measurements. Also presented are the first results on characterization of the skin electrode coupling achieved with the system.