Fig. 2b presents the electrochemical setup and the equivalent circuit for the measurement of electrochemical noise by an external measuring resistor, Rm. Here, V1 and V2 are the corrosion potentials of electrodes 1 and 2 respectively, measured with respect to a noiseless reference electrode. It is evident that the current can be calculated by either physically measuring the potential drop across Rm or by physically measuring the potentials V1 and V2 and taking their difference as the value of the potential drop across Rm. The second method has the advantage that any asymmetry between the circuit that measures potential and the circuit that measures current is avoided. For the traditional circuit, under the assumption of uncorrelated noise sources, the analysis is well known [3] and only the expression of the noise resistance is reported here for the general case of two electrodes (non-identical)Thus, in the usual case, if the two electrodes can be assumed to have identical resistances, the noise resistance provides an estimation of the electrode resistance. If a measuring resistor is added to the external circuit, one value of current and two electrode potentials are measured. The circuit of Fig. 2b, can be analyzed by the superimposition theorem, as graphically illustrated in Fig. 3. Thus, for the circuit of Fig. 3b, the current flowing across the measuring resistor is calculated by the usual equation for a current divider: