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The pressure is defined as the force exerted on the object. The force is applied perpendicular to the surface of the objects per unit area where the force is distributed. The basic formula of pressure is force per unit area (P = F/A), where pressure, force, and area are denoted by P, F, and A. There are various types of pressure, such as Absolute, Gauge, Atmosphere, and Differential pressure. In this article, we will discuss pressure and its types.

What is Pressure?

The amount of force acting on a unit area is known as pressure. It can also be known as the force to area ratio.

Formula and Unit of Pressure

The basic mathematical formula of pressure is:

Pressure (P) = Force (F) / Area (A)
P = F/A

The SI unit of pressure is Pascal (Pa), newton per square meter (N/m2), and pound per square inch.

1 Pa = 1N/M2

Types of Pressure

The following are the types of pressure:

  1. Absolute
  2. Gauge
  3. Atmosphere
  4. Differential

Absolute Pressure

The pressure related to a reference pressure in a vacuum is called absolute pressure. We can specify the absolute pressure where the measurements are needed, like barometer pressure, and where the equipment requires to remove all air. It is also known as Sealed pressure.

The formula for Absolute Pressure

Using a barometer, we can measure absolute pressure. It is equal to the total sum of the atmospheric pressure and the gauge pressure. The formula for Absolute pressure is:

Pabs = Patm + Pgauge

Where Pabs is Absolute Pressure,

Patm is Atmosphere Pressure,

Pgauge is Gauge Pressure,


Vacuum Pressure = Atmosphere Pressure - Absolute Pressure.

Gauge Pressure

It is the pressure relative to the pressure of the air. It is positive for pressures above the ambient pressure and negative for pressures under it.

The formula for Gauge Pressure

The Basic formula for Gauge Pressure is:

Pg = Pabs - Patm

Where Pg is Gauge Pressure.

Pabs is Absolute Pressure,

And, Patm is Atmosphere Pressure.

Atmosphere Pressure

The atmospheric pressure is defined as the pressure related to the atmosphere that surrounds the earth. This pressure is weather-dependent. Its sea-level value is 1013.25 Pa. It is also known as barometric pressure. A mercury barometer is used to measure the height of a mercury column that exactly balances the weight of an atmospheric column over the barometer. It can be expressed in many different unit systems, including millimeters (or inches) of mercury, millibars (mb), regular atmospheres, pounds per square inch (psi), dynes per square centimeter, and kilopascals.

Differential Pressure

The difference between the two points or pressures is known as the differential pressure. The differential pressure readings are assumed to all pressure readings because the pressure is measured as absolute pressure, vacuum, or gauge pressure to atmospheric pressure.

It is mostly used in industrial processing systems. It has two inlet ports for differential pressure gauges, and each port is connected to the volumes for that the pressure to be controlled.

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