ES337531A1 - Apparatus for remotely indicating the level of liquid in a tank - Google Patents

Abstract

The level of liquid in a sealed tank 2, Fig. 1, is indicated using a float 8 which comprises an annular magnet 9, housed in the float which is slidable along a non-magnetic steel tube 3, and an associated magnetic core 7 suspended on a stainless steel wire 5 from a disc 6. Between the disc and the core, the wire passes round a pulley 12 mounted on one end of a lever arm 13, the other end of which carries the core 16 of a differential transformer 17, which is thus positioned according to the wire tension. A counterweight 31 is arranged so that for a predetermined "equilibrium" tension, the core 16 is positioned centrally in the transformer 17. As the liquid level changes, the tension in the wire 5 and correspondingly the position of the core 16 will change accordingly due to the change in the Archimidean thrust on the float 8. A signal is thus transmitted from the transformer 17 to a two phase motor 21 which rotates the disc 6, via shaft 41, to re-position the float at the surface of the liquid. The amount of rotation of the shaft, indicating the change in liquid level, may be measured electrically, by mechanically connecting a three turn linear potentiometer (45), Fig. 2 (not shown), to the shaft 41, or pneumatically by controlling the pressure in a power relay 33 according to the rotation of the shaft. Alternatively a digital indication of the rotation of the shaft 41 may be obtained from a step-by-step motor (53), Fig. 3 (not shown), driven by pulses from the motor 21 and a photo-electric cell (56).