A free damping oscillation method for measuring electrolytic solution concentration by two electrodes

A conductivity detection method using two stainless steel electrodes by taking advantage of the free damping oscillation phenomenon is proposed. By electrically connecting an inductor and a capacitor to the two sensing electrodes, a second order resonant system is formed. When the resonant system is excited into free damping oscillation mode by a square wave pulse, its decay factor and natural frequency can be measured simultaneously. Experimental results, which are confirmed by numerical simulation, indicate that the decay factor is dominated by the electrical conductivity of solutions. When the peak voltage is adopted as measurand instead of decay factor, a simple electrical circuit can be implemented for online concentration measurement. NaCl solutions are used in experiments to verify the proposed method and satisfying results are obtained.