GB695058A - Improvements relating to the measurement of conductivity of liquids - Google Patents

Abstract

695,058. Measuring electrical conductivity of liquids. FIELDEN (ELECTRONICS), Ltd. May 2, 1952 [May 3, 1951], No. 10381/51. Class 37. A current is induced electromagnetically in the liquid under test and the magnitude of the current is measured as an indication of the conductivity of the liquid. In Fig. 1 the liquid flows through two glass tube branches 2, 3 forming a closed loop linking transformers 4, 5 so that branch 2 is the secondary of transformer 4 and feeds branch 3 forming the primary of transformer 5 whereby with change in conductivity of the liquid the secondary 7 of transformer J feeds a correspondingly varied voltage through an amplifier 8 to actuate an indicator 9. A balancing winding 10 may be provided and to avoid interaction the transformers 4, 5 may be staggered as shown, or at right-angles with in this case the tube branches skew. In a second arrangement, Fig. 2, the closed tube loop 12 forms a closed circuit secondary of a transformer 13 whose primary 14 constitutes the test variable arm of a normallybalanced A.C. fed impedance bridge. A change in conductivity of the liquid in the loop 12 produces a change in the reflected impedance of the primary 14 and thus a bridge out-of-balance voltage of phase sense corresponding to the sense of the change in conductivity of the liquid. This output voltage is fed to a phasesensitive amplifier 18 and Fig. 3 (not shown), whose output in turn drives a servo-motor 19 in the appropriate direction to adjust bridge zeroizing potentiometer 20 and move an indicator or pen 21 to indicate or record the change in conductivity. Fig. 2 may be modified to provide an arrangement wherein the transformer core and winding 14 covered with an insulating material are immersed in the liquid leaving the space within the core open.