others in essence impedence measures the response of the working electrode to a varying applied potential frequency in terms of electrical impedence current potential logging measures the current passing between two electrodes and the potential of the electrodes this data is then statistically analyzed the surface ph is dependent upon the cathodic current density and the rate of diffusion of alkaline species away from the electrode and the rate of diffusion of acidic species toward the electrode if the temperature surface geometry current density and flow characteristics of the brine or other fluid are known then by using fick 39 s laws of diffusion and basic chemical electrochemical equations the surface ph may be calculated control of the surface ph is less accurate using calculated values from diffusion laws e g fick 39 s law due to variability of hydrodynamics etc and would only be used as a u201c sighting shot u201d or to determine approximate settings for obtaining empirical data alternatively control values may be obtained from experimental data and used for other conditions by interpolation or extrapolation if the auxiliary and working cathode or sensing electrode are identical then they may be interchanged or the auxiliary may be used as a blank scale reference normal scaling potential reference an additional benefit of this technique is that electrode cleaning.