GB784729A - Improvements in or relating to liquid level indicating system - Google Patents

Abstract

784,729. Electric measuring systems. ARO EQUIPMENT CORPORATION. Aug. 18, 1955, No. 23814/55. Class 40 (1). Apparatus for determining the level of a volatile liquid inside a container by comparing the liquid and gaseous pressures inside the container comprises a moving diaphragm, pressure transducer controlling the slider of a potentiometer whose position is indicated electrically. The transducer comprises a two-part cylindrical chamber 20 (Fig. 2) with a diaphragm 36 clamped between the two parts. The upper part 30 of the chambercommunicates with the gaseous upper space in the main container, and the lower part 32 with the liquid, so that the diaphragm 36 moves in accordance with the difference in pressure on its face against a spring 74 mounted on a slidable rod 54 attached to the centre of the diaphragm. An earthed arm 112 is fixed to the inside of the lower part 32 of the chamber by a leaf spring 114 which presses the arm against a shoulder on an extension of the rod 54, so that as the diaphragm moves with a change in the differential pressure the arm 112 follows, and moves the slider of a potentiometer winding 80, the position of the earthed arm being indicated by a ratiometer instrument 3 (Fig. 4). The shape of the potentiometer 80 is made to correct for the non-linearities of the system, and the ratiometer then indicates the level of liquid in the main container. The shape of the upper part 30 of the transducer chamber 20 conforms with that of the extended diaphragm so that excessive liquid pressure does not distort the diaphragm.