Displacer type level transmitter

The liquid level raises and lowers a float. The float contains a magnet. The magnet operates a sensor, perhaps an array of reed switches or similar. The position of the magnet in the array is converted to a varying signal that represents liquid level, which appears on the terminals of the instrument.

actually displacer type technique is being used where level/flow is being measured along with the knowledge of quantity of the fluid.in this the instrument is 1st callibrated [for level measurement]with an amount of known liquid as how much liquid passes through the displacer if we go for any level gauges,and then by refrence of that data we go for real time application.

An example, If the process fluid i wanted to know the level of was H20. If the mechanical design of the instrument was to measure the buoyancy of the displacer to interpret level. If the displacer is completely out of the H20 the force of the displacer pulling down will be equal to the weight of the displacer. If the displacer is now submerged in H2O, then then force of the displacer is now less due to the buoyant force of the displacer in water. Don't get a displacer mixed up with a float.

Yes, do not get displacer mixed up with float. Float is just floating on the liquid. Displacer is submerge and buoyance in the H2O