Liquid level sensing device and swimming pool water circulation systems

Abstract

A liquid level sensing device is provided comprising, in combination, a U-tube having two substantially vertical legs in fluid interconnection at their lower ends; a variable capacitor in one leg of the U-tube, comprising two spaced electrodes receiving a dielectric liquid therebetween; a first mobile body in said one leg of a first dielectric liquid capable of rising and falling within the space between the electrodes and to a level at which it partially or fully fills the space; a second mobile body in said one leg of a second liquid having a higher density than and immiscible with the dielectric liquid, and having an upper surface on which rests the first body of dielectric liquid; a third mobile body in the second leg of a third liquid immiscible with the second liquid and disposed in operative relationship with the second body of liquid; and a fluid pressure communication between said third body and a fourth body of the same or different liquid whose liquid level is to be sensed, so that the relative level of said first body of first liquid in the space between the electrodes in the variable capacitor is related to liquid level in said fourth body, communicated as fluid pressure via the fluid pressure communication to said third body, and thereby moving the second body of liquid and the first body of liquid in the U-tube to a level related to liquid level in said fourth body and corresponding to a capacitance of the variable capacitor.