Pressure Switch

 Pressure switch


















Pressure Switch

is the device that measure the pressure and send it to the controller as a " Digital signal, Binary signal , Discrete signal 0 , 1 "

They are mainly used to send digital value when exceeding or falling bellow a limit value (set point)

Used for

•        Monitor (Alarm )

•        Protection (Cut off a process)

•        Control

 


Pressure switch types

  • Contact pressure gauge
  • Mechanical pressure switch
  • Electronic pressure switch 














Mechanical Switch vs Electronic Switch





How to select you device?

1.Basic Types

  •     For low pressure applications      (Diaphragm and Bellow)
  •     For medium and high pressure applications      (Bourdon tube and Piston)

 2.Expected Service Life time : (number of cycles the switch is expected to operate)

3.Speed of Cycling

     At extremely fast cycling (more than once every 3 seconds) a piston switch should be used because  bourdon tube or diaphragm switch  will heat and fatigue

4.Accuracy

 Diaphragm and Bourdon tube pressure switches generally have greater accuracy than (piston switches)

5.Adjustable Range  

       The set point should be in middle of (30% to 65%) of the adjustable range, For good life time

     6.Types of Switch Action

• Standard pressure switches sense a single pressure source and open or close a single set of contacts.

 • Differential pressure switches have two connections and sense the pressure difference across a circuit.

 • Dual switches sense a high and low limit on the same pressure source, and actuate two sets of electrical contacts.

7.Fluid Media

       The fluid compatibility with materials of construction must be considered. Consult switch manufacturers catalog.

8.Proof Pressure

      Proof pressure is the highest pressure that the switch will stand without permanent deformation.




 Pressure switch calibration

  • Exercise switch by checking its full range for 3 times.

  • Adjust increasing set point  (80 PSI) for example and detect the dead band
  • Decreasing the pressure till NC return to its normal position reset point (77 PSI)
  • Dead band:    80-77 = 3PSI (for example)

 

 

 

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