Float switch – how it works

Float switch is the basic form of a simple automation system. Its function is to operate or actuate a system by the level of liquid or fluid. 

Float switch can transmit only two types of signal - level zero & level high. 

A circuit can be design to start stop some process by receiving the signals from float switch. Common processes are sending low or high level alarm, starting or stopping pump motor.

Construction and working of float switch

There are two types of float switch constructed-Emptying type – On at floated upward position and off at clinging downward position. Filling type – On at clinging downward position and off at floated upward position.

Below images will clear the construction of float switch. It is designed to emptying a dirty water tank.

Dirty water level high- Level pump starts emptying, Dirty water level low-pump stops.

                                               Fig: Float switch off in a sump or sewerage tank

Water is at the bottom of the tank, float switch is downward position.

                                                    Fig: Float switch on in sewerage or sump

Water in sump is at high level, float switch position is downward.