GB256289A - Improvements in or relating to fluid pressure operated means for indicating the quantity and specific gravity of the liquid contents of tanks - Google Patents

Abstract

256,289. Martin, H. March 4, 1925. Indicators, electric.-The level of oil in a tank in which it is displaced by water is indicated at a distance by means controlled by variations in electrical resistance produced by the movement of two columns of liquid, and the specific gravity of the oil is also measured and the level readings corrected therefor. The apparatus is in two main portions, a transmitter A mainly constructed as described in Specification 231,595, and indicator B, preferably of the ratio coil type similar to those described in Specifications 164,828 and 219,716, [both in Class 40 (i), Electric signalling systems &c.]. Part of the variable resistance coil 13 is removed to the indicator B at 15, and part of the external fixed resistance 45 is placed adjacent to the resistance 15 at 17. The unit C is employed to compensate for specific gravity variations. The resistances 15, 16, are simultaneously controlled by a hand-operated arm 17 carrying a pointer 18 moving over a scale of specific gravities. The resistances 15, 16 are such that with both fully in circuit, a full-scale reading of B is obtained when the whole of the resistance 13 is short-circuited by immersion in the mercury, and when both are cut out by the arm 17, a full-scale reading of B is obtained with half the resistance 13 short-circuited. To obtain the specific gravity of the oil in the tank, a pair of insulated contacts 25 are inserted in the tank at the " ¥ full " position, and are connected through a switch and battery to a galvanometer 29, a corresponding mark being made at the "¥ full." position of the indicator B. When the tank is being filled, the contacts 25 are opened when reached by the oil, and the arm 17 is then adjusted until the scale reading on the indicator is ¥ " full." The reading on the scale 19 then indicates the specific gravity, and accurate readings of level are obtained on the indicator B as long as the specific gravity remains constant. A change in specific gravity necessitates a re-setting of the arm 17. If applied to an ordinary storage tank without water displacement, the contacts 25 would be placed at the top of the tank, and would indicate " tank full."