• ##### Basic Instruments

In this section we will read about

## Instrumentation

### Pressure Switch

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In this lesson, we will study pressure switch

• A pressure switch is a form of switch that makes electrical contact when a certain set pressure has been reached on its input.
• This is used to provide on/off switching from a pneumatic or hydraulic source.
• The switch may be designed to make contact either on pressure rise or on pressure fall.
•     This is a device designed to monitor a process pressure and provide an output when a set pressure (setpoint) is reached.
• A pressure switch does this by applying the process pressure to a diaphragm or piston to generate a force that is compared to that of a pre-compressed range spring.

• The construction diagram of Pressure Switch is shown in the above figure.
• Main Parts of Pressure Switch are

A) Electrical Connection: Electrical Connections are made at this point.

B) Adjustment Screw: Adjustment Screw is used to adjust the set point of Pressure Switch.

C) Switch contact: Switch Contact is used for making NO (Normally open) and NC (Normally Closed) contacts on Pressure rise or fall.

D) Pressure Connection: Pressure Connection is used to connect the Pressure switch in a body, line, tank or Process.

Operation of Pressure Switch

Pressure Switch has 3 contacts.

• Common
• NO (Normally Open)
• NC (Normally Closed)
• A spring is used in pressure switch when pressure increases this spring comes in tension. The pressure is also set using adjusting screw when increasing or decreasing pressure comes to this pressure contact changes from NC to NO or from NO to NC.

• Differential pressure is also used In pressure Switch. In this pressure Switch, two Pressures are used.

1.Differential Pressure.

2.main Pressure.

Let Suppose the main Pressure is 4kg/cm^2 and Differential Pressure is 1 kg/cm^2, then on increasing pressure contact will change from NC to NO at 5 kg/cm^2 and on decreasing pressure from NO to NC at 3 kg/cm^2.

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