Float and Board is a simple economic level measuring instrument for large non pressurised storage tank. Its is a simple float and counter balancing mechanism, float inside the tank and counter weight (scale pointer) connected by the rope wire which is moving freely on the pulley assembly.

The principle of float type level meter is that a float moves up and down due to buoyancy. A reed switch in a stem is actuated by a magnet in the float, and outputs detection signal (see the figure below). However, the level meter may not measure liquids with some viscosities and specific gravities.