GB675080A - Apparatus for indicating percentage change in concentration of a solution - Google Patents

Abstract

675,080. Electric tests and measurements. WILKINS, S. R. Nov. 8, 1950 [Nov. 8, 1949,] No. 27164/50. Divided out of 675,030. Class 37. Apparatus for indicating changes in the concentration of a solution by corresponding changes in its conductivity comprises a bridge circuit wherein a cell 17 (Fig. 1) consisting of two electrodes in the solution to be tested, in series with a standard reference impedance 16 is connected across an A.C. supply from a transformer winding 12, a proportion of the unbalance voltage selected by a potentiometer 21 being taken to the grid of a thyratron 18 fed with A.C. on the anode from another winding 13 of the transformer 10, and containing a relay winding 19 in the anode circuit. The grid of the thyratron is biased with A.C. from a potentiometer 20 across a further transformer winding 11, so that at and above a certain out-ofbalance current the thyratron fires and operates the relay 19. In a modification (Fig. 2), the bridge circuit is replaced by a potentiometer circuit, the cell 17 and the standard impedance 16 being connected in series across the A.C. supply from a winding 31, and a proportion of the voltage across the standard impedance 16 is selected by a potentiometer 35 and fed to the grid of the thyratron 33. The thyratron will thus fire at a reduction of concentration of the solution determined by the adjustment of potentiometer 35, which may alternatively be connected across the cell 17.