GB723949A - Improvements in electrical indicating systems - Google Patents

Abstract

723,949. Electric indicating systems. SANGAMO WESTON, Ltd. Oct. 13, 1952 [Oct. 15, 1951], No. 25618/52. Class'40 (1). Apparatus for indicating the level of a liquid comprises two circular potentiometers, one in each of two interconnected bridge circuits, arranged so that the full scale reading of the indicator of one bridge is equal to one unit reading of the other bridge, the larger indicator pointer moving in discrete units as the more sensitive indicator pointer falls below zero of goes beyond the full scale indication. Movement of a float F (Fig. 2) on a liquid L causes rotation of the slider 15 of a potentiometer 16, and a geared rotation of slider 17 of a second potentiometer 18. The slider 15 can make a plurality of rotations, the wire of potentiometer 16 covering 360 degrees with a small open-circuit portion. The potentiometers 16, 18 are included in two DC bridge circuits (Fig. 1) having moving coils 43, 55 respectively in the diagonals to indicate the unbalance currents on meters 44, 33 respectively, the former diagonal containing a bucking coil 56 coupling with the moving coil 55 of the second diagonal, the coupling being such that as pointer 46 of meter 44 moves from zero to full scale, the unbalance current in bucking coil 56 opposes the increase in current in moving coil 55, and maintains the pointer 36 of meter 33 stationary. At the ends of the scale of meter 44 slider 15 of potentiometer 16 is open-circuited and the pointer 36 of meter 33 jumps to the next discrete unit indication.