The present invention relates to an electrode assembly that is capable of both solution measurement and in-line self-cleaning. Specifically, such electrode assembly comprises a central electrode and a measurement circuit for solution measurement, and an auxiliary electrode and an auxiliary current sourse for generating gas during intervals between solution measurement cycles, so as to remove any solid or liquid residues that may passivate the central electrode, thereby cleaning and rejuvenating the central electrode and preparing it for the next solution measurement cycle.