Pressure Switches

Pressure switches are activated by change in the pressure of a gas or liquid. Based upon the action of the transducer the pressure switch devices are used to convert the pressure change into the linear or electrical energy based.

Based on the application of the pressure increasing and decreasing the switches can be made to turn ON.

Pressure switches are divided into two types they are

  • Pneumatic pressure Switches
  • Hydraulic pressure switches

In the pressure switches are available in contact type and non-contact type. When coming to the contact type the unit must be placed within the unit physically, for the pressure to be gauged. For non-contact type systems they use innovative equipment to measure the pressure, and other sensors are placed outside of the container.

Pressure switches are available in different ranges and settings. Based upon the application one needs to choose the proper pressure switch.

Basic parts of the pressure Switch:

The pressure switch consists of Micro switch, Insulated trip button, operating pin and operating piston, trip setting nut, range spring and housing.


Micro switch

When the pressure switch is operates the micro switch is used to break or make and electric circuit. The switch is made up of open and close contact. When the switch activates, then the open contact becomes close and the close contact becomes open. During the low current applications and low currents gold contact micro switches are used. Based on the high currents and voltages silver contacts are used.


Insulated Trip Button

When the pressure switches are activated, in that process turn-on button causes the opening and closing contact of the switch.

Operating pin

In the system the operating pin is attaches to the operating piston. When the piston stimulates, at that instance the inlet pressure must be changed. Based on the process the pin must be moved upwards and contact between the trip button and in the same way the when the pin moves downwards it disconnect with the trip button.

Operating piston:

In this process the pressure switch must be in contact with the piston. The piston generates the force when the pressure acts on the area and the forces opposes the range spring simultaneously. The range of switch is known as the operating piston area and range spring rate. Mainly they are measured in N/mm and lbf/inch.

Trip setting nut

It is also known as the range screw. It is used to adjust the pressure switch set point. If the compression is higher in the range spring, then the pressure set up in point of the switch is also high. In the same way, if the compression of the spring is lower at that illustration, the pressure switch set up point is lower.

Range spring

Range spring is a pre compressed spring when the forces are generated where the pressure is determined.


All the equipment placed in enclose is known as housing. The pressure switch gives out an electrical output in one or more tapped networks are also provide to permit the cable to carried in to the switch case through proper gland. For the pneumatic switches two are more bulk head connections are arranged for the output connections. The housing is available in the form of stainless steel and aluminum.


Working of pressure switch:

The inlet pressure is applied on the operating piston, this is to apply the force on the piston in the upwards direction and against the range spring. At certain pressure point the tension of the range spring can be adjusted and then compressed. When it reaches the required pressure at such instance the operating pin on the micro switch hits the trip button to change it over. In the process, the open contact will be closed and the closed contact will be opened. By adjusting the trip nut settings the micro switch changes over the pressure, simultaneously the tension of the range nut is to be adjusted.

Hydraulic pressure switches


In many cases, the pressure switches are in contact where they usually fit into the container to measure the liquid pressure. They are very small in unit and the dislocation of the unit is allocated into the measurement. The unit consists of two sections they are transducer and switch unit.

The transducer unit consists of equipment, which is used to measure the pressure that is present in the container. This is to identify according to the ascending and decreasing of the pressure. In other equipment we observe the multiple points pressure set up. The pressure meets the setup pressure, where the transducer unit must send the signals to switch unit. The switch unit converts the signal in to the electrical energy. The received energy generates the step in the application. In the fuel gauge the pressure gets low at that at theta instance a warning light is generated by using the electrical energy it is activated. The scientist’s use monitor pressure to prevent the exposition occurred in the rockets.

Some types of the liquid are viscous in nature, and basic switches are not correctly adjusted to the liquid type. The hydraulic pressure switches can handle many types of the hydraulic liquids that are designed to handle the pressure at different levels. Mainly they are operated at the 300 to 2600 PSI, and can also stand at the temperature of 4000, 12000 Psi, as they are available at very high costs.

Applications of hydraulic pressure switch:

  • Hydraulic pressures are mainly used in the automobiles.
  • When the oil pressure falls below the safe level, in that process warning light indicates the fall down of the oil pressure.
  • A switch is arranged on the header when the air pressure is less than the requirement, and the alarm is generated at such instance.
  • In the air craft’s, the hydraulic system are used to operate the lights, coolants present in the system, plane flaps and landing gear.
  • In space crafts and satellites arrangement, the switches are very important.
  • Improper monitoring of the pressure leads to the explosion of the vehicles.
  • Rocket propulsions mainly depend on the direction of the pressure released where the arrangement of switches is important.

Applications of pneumatic pressure switch valve:

  • When there is no need of the suction stage, there is a chance of gas compressor turn-off.
  • Used in a battery charge control

Other types of the pressure switch are

High pressure switch

Mainly the high pressure switches are designed for the requirement of the heavy duty air compressors. They are made up of painted stainless steel and cover attacks, the tough environments encountered in industrial uses. The highest pressure must be 400PSI

Diaphragm pressure switch

To control the liquid level various effluents, sumps, and sewage applications are available. Different switch settings are available for to turn-on and turn-off the pump. The design of the diaphragm pressure makes it more dependable than traditional float ball machinery.

Low pressure switch

The low pressure switches are mainly used in the food waste disposer, swimming pool pumps and spas, hot tubes, medical equipment, outdoor machinery etc. The engine consists of a control box where a remote control switch is arranged. The operating pressure of the low pressure switch ranges from 20 to 1000mbar

Liquid level pressure switch

It is used to control the water level or other dangerous liquids. The liquid level pressure switch is similar to the diaphragm pressure switch. It operates at a range of 10 to 85

Air compressed pressure switch

It is used to regulate the pressure of the tank between the preset valves. The operating pressure of the air compressor pressure switch is 25 to 175 PSI.

Application of pressure switches:

For detecting the pressure change pressure switches are used to set point or predetermined level. They act as

  • Steam turbines
  • Safety devices
  • Boilers
  • Alarms
  • Water level control
  • Stem power plant
  • Pumps
  • Electronic motor
  • Automobiles
  • Gas compressor

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