US Patent 9615761 Methods and apparatus for measuring individual electrode impedances

Electrode impedances on a body of a subject are measured by connecting a sense electrode, a reference electrode and a return electrode to the body, using the sense electrode to deliver a test current from a current source to the body of the subject, and measuring the potential difference between the sense electrode and the reference electrode. The impedance of the sense electrode on the body is measured in accordance with the measurement of the potential difference between the sense electrode and the reference electrode.