Pressure switches are used to detect the presence of pressure in industrial systems using pressurized fluids. Pressure switches contain a piston or diaphragm that moves when pressure reaches the switch's set point, triggering electrical contacts to open or close. There are normally open and normally closed contacts, such that when pressure reaches the set point the normally open contact closes and normally closed contact opens. Pressure switches can be calibrated by connecting them to an air source and pressure gauge and adjusting the tension spring to set the trigger point for contact switching at the desired pressure level.

1. Pressure Switch
Instrumentation
Knowledge

3. Pressure is form of switch that change
the electric contact when Pressure
Reached at their Set-Point. Pressure
switches are widely used in industry
to control systems that use
pressurized fluids. Pressure Switch is
On Off device that use to detect the
Presence of Pressure.

4. Look at the internal diagram of Pressure
Switch, Pressure Applied on the Bottom
of Operating Piston { Like Diaphragm ,
Bellows, Capsule , or Bourdon Tube }
Then the Piston try to move upward
against the Tension on Spring. The
Tension range of the Spring can be
adjusted So the spring compressed at
Certain Pressure. And this is called the
set-point of Pressure Switch. When
Pressure Reached To set-point the
operating Pin hit the Trip button and
change it over.
So the Normally Open Contact will
Become closed and the Normally Closed
Contact will become open.

6. There Are Two Electrical Relay Contact in Pressure Switch.
I. Normally Open
II. Normally Close
When the Pressure Reached at Set point ,the Normally Open
Contact will Become closed and the Normally Closed Contact will
become open.

7.  PRESSURE SWITCH CALIBRATION ;

8.  PRESSURE SWITCH CALIBRATION ;
1. Connect the Pressure switch to Air
Source or Hand Pump via Pressure
Gauge.
2. Use Digital Meter to Check the Switch
Contact are as Indicated. NO NC
3. Connect Meter to Common and
Normally Open , The meter Indicate
Open Circuit. Then Increase air
Pressure until the Contact Change and
Meter Read Short Circuit. And Note the
Pressure Reading.
4. And Reduced The Pressure until the
Contact Change . And Note the falling
Pressure.
5. The Difference Between Raising and
Falling Pressure is called Dead Band.
6. You can set Pressure as Demand by
using Trip setting Nut.

9. THANK YOU
Regard ;
Instrumentation Knowledge