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Before leaning of Unit of pressure , it is important to know about pressure and pressure measurement. The pressure measurement is the most common of all the measurements performed on the system. Pressure is widely used along with flow measurement in industry, laboratories, and many other fields for a variety of reasons. Pressure measurement is not only concerned with the determination of force per unit area, but is also involved in many liquid level, density, flow and temperature measurements.
Pressure
The pressure is a force per unit area exerted by a fluid perpendicular to a boundary (as opposed to shear stress, which is exerted parallel to the boundary.) Daily pressure measurements, such as the pressure in a car tire, are usually made relative to the ambient air pressure. Other times, measurements are taken in relation to a vacuum or some other arbitrary standard. The following words are used to distinguish between these null references:
Types of pressure
There are four types of pressure that is given below
( I ) Atmospheric pressure
The pressure caused by the air around the surface of the earth is called atmospheric pressure.
(ii) Absolute pressure
Pressure is defined as force per unit area. When the interactions of liquid particles are zero, there will be zero pressure intensity. This is possible only when the population of molecules is negligibly small, which means a complete vacuum. Therefore the intensity of pressure measured from the condition of prefect vacuum is called absolute pressure. So it is equal to gauge pressure and atmospheric pressure
(iii) Gauge pressure
A pressure measuring instrument typically measures the difference between the unknown pressure (P) and the atmospheric pressure (PATA). The pressure that the instrument measures is known as gauge pressure when the unmeasured pressure (P) is higher than the atmospheric pressure (Patm). Gauge pressure refers to zero against ambient air pressure, so this absolute pressure is equal to zero atmospheric pressure. Negative signs are usually omitted.
(iv)Vacuum pressure
A pressure measuring instrument typically measures the difference between the unknown pressure (P) and the atmospheric pressure (Patum). When the atmospheric pressure (Patm) is greater than the unknown pressure (P), the pressure measured by the instrument is called vacuum pressure.
Unit of pressure  What is the SI Unit of Pressure?
The SI unit for pressure is the pascal (Pa), equal to one newton per square meter (N·m−2 or kg·m−1·s−2). This name for the pressure unit in SI was added in 1971; before that, pressure in SI was expressed in units such as N/m².
Pascal Formula:
What is the CGS Unit Of Pressure?
The CGS unit of pressure is barye (Ba), equal to 1 dyn·cm^{−2}, or 0.1 Pa.
Conversion of one unit into other
Pascal

Bar  Technical Atmosphere  Standard Atmosphere  Torr  Pound per squareinch  
Pa  bar  at  atm  torr  lbf/in^{2}  
1 Pa  1 N/m^{2}  10^{5}  1.0197*10^{5}  9.8692*10^{6}  7.5006*10^{3}  0.000145037737730 
1 bar  105  100 kPa  1.0197  0.98692  750.06  14.503773773 
1 at  98066.5  0.980665  1 kgf/cm^{2}  0.967841105  735.5592401  14.223343307 
1 atm  101.325  1.01325  1.0332  1  760  14.695948 
1torr  133.32296842  0.001333  0.00135951  0.00131578  1 mmHg  0.019336775 
1 lbf/in2  6894.757293  0.068947  0.0703069  0.06804596  51.7149325  1 
Frequently Asked Questions – FAQs
What is pressure?
The pressure is generally started as the amount of force that is exerted on a certain area.
What is the formula of pressure?
Pressure is usually represented by the formula p = F/A. Here, ‘F’ is the applied force, and ‘A’ is the area of the region.
What is the SI unit of pressure?
Pascal is the SI unit of pressure.
Define one Pascal.
One Pascal is defined as one newton per square metre.
What is the CGS unit of pressure?
The CGS unit is barye (Ba). It is equal to 0.1 Pa.
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