Sensitivity in Local Concentration Fluctuation Measurement with Micro Electric Cell

Abstract

Sensitivity of the electrode in detecting the concentration mass of strong electrolyte solution was analysed numerically for the case of a single mass in an electric field between a large spherical or ring electrode and a concentric micro-spherical electrode. The response curve is spike shaped (large mass) or mountain shaped with a gentle slope (small mass) when a mass grazes a micro-electrode.
The more a mass covers and passes concentrically through the micro-electrode, the more the slope and peak of the response curve are sharpened and the peak is flattened. The peak value, I_M, is not only a nonlinear function of the mass concentration, but also a function of mass size. The real concentration of mass is larger than that estimated from assuming I_M lineally proportional to the concentration.
On the contrary, beyond the middle stage of turbulent mixing, where there are many of relatively large mass in high level of background concentration between electrodes, the peak value I_M, though small, is approaching to direct proportionality to the concentration. Therefore, the reliability of electrical measurement of the concentration fluctuation is good in the final stage of mixing.