Measurement and monitoring of the electrical conductivity of liquor samples

A measuring cell for use in measuring and monitoring the electrical conductivity of a liquid, comprising at least four concentric circular electrodes disposed in a surface and mutually separated by annular areas of electrically non-conductive material, said surface being flat and being supported by a main body portion of the cell, the body portion being adapted to be mounted in a vessel or machine for presenting said surface, and hence the concentric electrodes, to a liquid under test, the body portion being tubular but not itself forming an electrode, the electrodes being respectively defined by one end of each of a plurality of cylindrical metallic members coaxially disposed within the tubular body portion and mutually spaced apart by tubular spacers of electrically non-conductive material, and the central, inner electrode being hollow to receive a temperature sensitive element.

A system for monitoring the electrical conductivity of a liquor sample, comprising a measuring cell having at least four concentric, circular electrodes disposed in a flat surface and mutually separated by annular areas of electrically non-conductive material, said surface being presented, in use of the system, to said liquor sample under test, a high impedance alternating current source connected across a first pair of said electrodes, means for producing a direct current signal which is dependent upon the alternating voltage across a second pair of said electrodes comprised by electrodes intermediate said first pair, means for deriving a control signal from said direct current signal and applying the control signal to said high impedance alternating current source to vary the current applied to said first pair of electrodes in dependence upon the conductivity of the liquor sample, and means for measuring said current applied to the first pair of electrodes to derive a signal dependent upon the conductivity of the liquor sample.

A system for comparing the electrical conductivities of two liquor samples, comprising a pair of electrode cells, one for presentation to each of the two liquor samples, respectively, each cell having at least four concentric, circular electrodes disposed in or on a substantially flat surface and mutually separated by areas of electrically non-conductive material, said surfaces being presented, in use of the system, to said two liquor samples, respectively, a pair of high impedance alternating current sources respectively connected across a first pair of the electrodes of the cells, means for producing respective direct current signals which are dependent upon the alternating voltages across second pairs of said electrodes comprised by electrodes intermediate said first pairs, means for deriving a control signal from the direct current signal from one of said cells and applying this control signal to both the high impedance alternating current sources to vary the current applied to both said first pairs of electrodes in dependence upon the conductivity of the liquor sample in contact with said one of the cells, and means for comparing the two direct current signals from the second pairs of electrodes to provide a signal which depends upon the conductivities of the two liquor samples.