Tecfluid - Model LP Series - Level Displacers - Brochure

According to Archimedes principle of body submerged in a liquid. A float with a density similar to the measured liquid is suspended by a spring to maintain an equilibrium with its weight. This float is always submerged in the liquid (not floating on the surface). A variation in the liquid level  produces a change in the weight of the float (partially submerged), which can be measured by the extension or compression of the spring that supports the float . The variation in the length of the spring is transmitted to the indicating needle via a magnetic coupling .