Float actuated devices measure liquid level using a float, which lies on the surface of the liquid and changes its position as the liquid level varies. Fig. presents a schematic view of a float-actuated device.
The level of the liquid 1 in the tank 2 is under measurement. A sensitive element 3 (a float of a cylindrical shape) is placed on the surface of this liquid. This sensor is connected through a cable 4 and two rotating wheels 5 with a balancing weight 6. A position of the balancing weight and a pointer 7, attached to it, in respect to a scale 8 determines the level of the liquid in the tank. Density of the float should be less that that of the liquid. Usually, plastic materials are used for manufacturing of floats
pplication of these devices assumes that the float is immersed in the liquid by the middle of its height. Therefore, when density of the liquid changes an error introduces into results of level measurement.
These devices have a simple design, high accuracy, wide range of measuring levels and the possibility of level measurement for aggressive and viscous liquids. However, they are not able to measure levels in tanks under pressure.