Float Sensor
When the magnetic field of permanent magnet inside the float is moved into to the proximity of the reed switch inside the stationary stem, the reed switch "snaps" the contact together and closes the electrical circuit. When the magnetic field is moved away from the reed switch, the reed switch does not touch. The circuit is open.

Flotation sensor wiring is pretty straightforward. There are only two wires. The switch in the sensor is normally open. To make an effective NPN switch one wire is connected to ground and the other to the input of the control. To make a PNP connection, one wire is placed to the supply voltage (usually +24VDC) and the other wire is connected to the control input. It is strongly advised not to wire AC or voltages higher than 24V to the sensor because of the presence of liquids, an electrical hazard might exist

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