Operation is based upon simple buoyancy, whereby a spring is loaded with weighted displacers which are heavier than the liquid. Immersion of the displacers in the liquid results in buoyancy force change, which moves the spring upward. Since the spring moves only when the level moves on a displacer, spring movement  is always a small fraction of the level travel between displacers .A  magnetic sleeve is connected to the spring and operates within a non-magnetic barrier tube  .