What is pressure switch?

Pressure switches are used to make or break (open or close) electrical circuits at selected pressures to operate solenoid-operated valves or other devices used in the system. 

A pressure switch is used to detect the presence of fluid pressure. Most pressure switches of a diaphragm or bellows as a detection element. The movement of this sensor element is used to activate one or more switch contacts to indicate an alarm or to indicate or initiate a control alarm.

Operating principle of Pressure switches:

The operating principle of a pressure switch is shown below.

This design contains two separate electrical switches. Each one is operated by a push rod that bears against a piston whose position is controlled by hydraulic and spring forces. The pressure at which the switches operate is selected by turning the adjusting screw to increase or decrease the spring force.

It should be noted that in this design the switches are actuated by the springs when the unit is assembled. Thus the normally open contacts are closed and vice versa.

When the preset pressure is reached the plunger will compress the spring and allow the push rods to move down causing the snap action switches to revert to their normal condition.

By using both switches in conjunction with an electrical relay, system pressures may be maintained within widely variable high and low ranges.

Uses of pressure switches

• Uses in limiting pressure

• It is used to operate as a safety valve, which vents out pressure when the pressure exceeds the upper limit

• Pressure switches are used in: Boilers, Gas compressor, Automobiles, pumps, steam turbine, Steam power plant. 

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