An instrument designed to measure the electrical impedance between the surface of external electrocardiography electrodes and the skin; it is also typically capable of measuring interference voltages that may be stored on electrodes (i.e., offset voltage) and/or detect faulty lead wires and cables. The device is mainly used to assess the ability of a set of surface (skin) electrodes to conduct bioelectric signals from the skin to the electrodes; it can also measure the impedance of the lead wires and cables from the electrodes to the measuring unit. It is intended to be used by a healthcare provider in a clinical setting.