Caustic monitoring and control system and probe

摘要

Sensor assembly and system for sensing conductivity and thereby controlling the concentration and level of a solution includes first and second probes adapted to be at least partially immersed in the solution whose conductivity is to be sensed. The probes are fixedly supported in a predetermined geometrical relationship with respect to each other in an externally mounted housing. Each of the first and second probes has an outer insulative sheath and an inner conductive electrode, the electrodes being exposed to the solution at least one point when their probes are immersed therein. At least one of the electrodes is recessed a predetermined distance from an open end of its respective sheath so that the solution must fill a predetermined volume in the sheath corresponding to the predetermined distance before contacting the electrode. The probe including that one of the electrodes has a clear path therethrough to permit solution to rise therein to a level of the electrode. The resistance between the two probes is a function of the conductivity of the solution between the two probes, this solution in the predetermined volume in the one probe providing a substantial portion of the total resistance between the two electrodes. An alternating current waveform is applied across the first and second probes to determine the resistance therebetween.