Analysis Between Vacuum Degree, Gauge Pressure and Absolute Pressure

Absolute pressure refers to the pressure directly acting on the surface of the container or object, that is, the actual pressure that the object bears. Its zero point is absolute vacuum, the symbol is Pabs.

The pressure caused by the thick atmosphere surrounding the earth's surface acting on the earth's surface or surface objects is called "atmospheric pressure", and the symbol is B.

The pressure measured with pressure gauges, vacuum gauges, U-shaped tubes and other instruments is called "gauge pressure" (also called relative pressure).

The "gauge pressure" starts from atmospheric pressure and the symbol is Pg.

The relationship between absolute pressure, atmospheric pressure and gauge pressure is: Pabs=B+Pg   

There are three ways to express pressure, namely: absolute pressure, gauge pressure, negative pressure or vacuum degree.

  • Absolute pressure is the actual pressure the object bears, and its zero point is absolute vacuum.   

  • Gauge pressure refers to the difference between absolute pressure and atmospheric pressure.   

  • The vacuum degree refers to the absolute value of the negative pressure value. When the absolute pressure value is less than the atmospheric pressure, the gauge pressure is negative ( ie negative pressure).   

The legal unit of pressure is Pa, and the bigger unit is megapascal ( MPa )=10^6Pa   

1 standard atmospheric pressure=0.1013MPa   

In the old unit system, the pressure unit is kgf /cm2 (kg/square centimeter), 1kgf/cm2=0.098MPa   

gauge pressure (relative pressure) unit: MPa (G)  

Absolute pressure unit: MPa (A)   

Absolute pressure: relative pressure + atmospheric pressure = absolute pressure   

Relative pressure+0.1=Absolute pressure,0.1 should be based on local temperature changes, longitude and latitude considerations, the actual value will be 0.5PA lower than measured value.   

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