Hitachi, Ltd.

Koji Tsutsuta

Kiwao Seki

An electrical conductivity measuring apparatus for measuring the electrical conductivity of liquid has a plurality of electrodes disposed in the liquid contained in a measuring cell, with an a.c. voltage being applied between the electrodes, thereby measuring the electrical conductivity by measuring a current flowing between the electrodes. The apparatus includes a reference a.c. voltage source including adjustment means for varying the magnitude and phase of the signal current, and is designed to cancel the conductivity of background by adding the current from the reference a.c. voltage source to the current from the electrodes.

Apparatus for measuring electrical conductivity

A conductivity detector includes an A.C. voltage supply and control circuit for applying a pair of electrodes disposed within a cell filled with electrolyte with a predetermined A.C. voltage and a correction signal generating circuit for generating a A.C. reference signal. At an auto zero adjustment operation, an output A.C. current signal flowing through the electrolyte is detected and the A.C. current is added to the A.C. reference signal. In advance of measuring conductivity, the amplitude of the A.C. reference signal is corrected until the resultant signal of the A.C. output current and the A.C. reference signal reduces to zero.

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Katsuta, Japan

Koji Tsutsuta