To keep the level of water or any form of liquid constant in storage tanks, a float switch or a level switch is used. It is a very crucial switch. If and when the switch malfunctions, the whole town could be out of water or the whole production line can go down. So constant checks and maintenance are usually called for.
First let’s describe the float switch. The float switch naturally come with a float. This float has a switch attached to it in such a way that when water is low, the float will slant to one side, closing the circuit which will trigger an alarm, informing the technicians that water level is running low or it might automatically start a water pump to start pumping water into the tank from other sources. The contact points inside s float switch is worth a mention as it is not made from the usual copper strip that we see. This switch has terminals that are located on each end of a small cylinder. Inside this cylinder it is half filled with mercury. Mercury is a very good conductor of electricity. When the float slants to one side when water level is low, the mercury will naturally flow to the low side of the slant, thereby linking the two terminals together, effectively closing the circuit to trigger whatever it has been set to trigger.
The level switch however works on a different principal, this time using the water in the tanks as the main conductor of electricity to trigger the alarm. While the float switch has to be dipped in the water, the level switch is attached to the top of the tank. From the switch, two highly conductive rods are then dipped into the liquid. The length of the rods are adjusted according to which level the users want the alarm triggered or the pumps to be started. As we know, water is also a very good conductor of electricity. These two rods are electrically connected by a very low voltage current when it is dipped into the water, just enough to close the circuit and not pose any danger to living things. When the level of water dips below that rods, the circuit will be broken and it will trigger the alarm.