Abstract: An apparatus and method for obtaining a measurement of various qualities of an electrochemical cell. The apparatus includes first and second electrodes and an excitation source for providing a time varying excitation voltage to the first electrode. The excitation voltage is switched between two voltage levels with the first and second voltages alternately applied to the first electrode for predetermined times. An external capacitance is connected between the second electrode and ground. The apparatus is capable of determining the time related rates at which electrical charge is transferred from the first electrode to charge the external capacitance. These rates, here termed Transient Immitivity Response (TIR), may be provided as a digital or analog output.