A displacer is fixed on a stainless steel cable. Its density is higher than the measured density. So it always prolongs the spring. Under free condition, the spring is prolonged to preset length and keep the spring within certain elastic limit by a stainless steel stopper. The first magnet is located in the spring guide rod and moves up and down as the spring expanding or contracting.
There is an up/down adjustable switch outside pressure pipe in the housing. As liquid level rising and the displacer immersed, the increased volume of buoyancy force is equal to the weight force of displaced liquid volume by Archimedes principle. As spring elastic force diminishing and spring constriction, the first magnet will move up to trigger the mechanical switch. When the liquid level decreasing, displacer emerges from liquid level, spring receives that added force, and spring increases to a certain length, the first magnetic switch move and the switch is reset to former state by action of first magnetic switch.
Height up to 20 Mtr