A Leveltrol in an instrument used for measuring the liquid level between two known points. The Leveltrol works on the buoyancy principle. Leveltrol has a float, which submerses proportionately with liquid level rise in the float chamber. The amount of submersion of the displacer depends on the liquid density, which produces a torque. The amount of torque produced in measured in terms of % of a level.
Parts of Leveltrol:
Float chamber, Float, Torque lever, Knife edge, Feedback Bellows, Air Relay, Restriction, Flapper, Nozzle, Feedback link, Density range, Action change lever, HP, and LP flange,