Fig. 4
Setup for contact impedance measurement \( (Z_{contact}) \). a Circuit to calculate combined impedance \(Z_{sum}\), it is equal to the sum of both, tissue impedance (skin impedance and subcutaneous tissue) and contact impedance due to electrode 2 (\(Z_{contact}\)). b Circuit to calculate impedance \(Z_{23}\), it corresponds to sum of tissue impedance (skin impedance and subcutaneous tissue), contact impedance due to electrode 2, and contact impedance due to electrode 3