What's the Difference Between Gauge Pressure and Absolute Pressure?

TIME: 2025.04.16 AUTHOR: Admin NUMBER OF VIEWS ~~2285~~

Pressure measurement is an integral part of industrial manufacturing. We monitor pressure values to ensure that industrial production is safe, efficient and smooth. Two important concepts in pressure measurement, gauge pressure and absolute pressure, are different types of pressure. Understanding the difference between the two is crucial for many fields, such as industrial production, scientific research and even some applications in daily life.

What is gauge pressure?

Gauge pressure refers to the pressure value relative to the local atmospheric pressure. Therefore, the gauge pressure is also called relative pressure. The local atmospheric pressure value is taken as the zero point. The value above the atmospheric pressure is positive pressure, and the value below the atmospheric pressure is negative pressure. For example, the pressure value displayed by a car tire is the pressure value relative to the local atmospheric pressure, which is the gauge pressure.

What is absolute pressure?

Absolute pressure is a pressure measurement method that takes absolute vacuum as the zero point. In a closed device, if the air is extracted and the pressure is infinitely close to vacuum, the absolute pressure value of the pressure system is 0. Therefore, in our normal pressure environment, assuming that our environment is 1 standard atmospheric pressure, then the absolute pressure value is 101.325kPa (one standard atmospheric pressure).

Gauge pressure Vs Absolute pressure

Reference baseline

Gauge pressure and absolute pressure are different in pressure baseline. Gauge pressure takes local atmospheric pressure as baseline value, while absolute pressure takes absolute vacuum pressure as zero point. Therefore, the relationship between gauge pressure and absolute pressure can be expressed as: PA=Pg+Patm, Pg=Pa-Patm. The relationship between them can be shown as follows:

Value changes

The gauge pressure value has a significant relationship with the local atmospheric pressure value. The increase or decrease of atmospheric pressure value will have a slight effect on the gauge pressure value. However, the absolute pressure will not have such an effect. The absolute pressure uses the pressure value of absolute vacuum as the zero point reference. Therefore, the local atmospheric pressure will not affect the absolute pressure value. As long as the gas state in the closed container does not change, the absolute pressure value is fixed.

Units

Generally speaking, gauge pressure and absolute pressure usually use the same international units, such as Pa, kPa, MPa, etc. However, in some cases, absolute pressure may use atm as the unit, while gauge pressure generally does not use atm as the unit. They often express the difference relative to a standard atmospheric pressure.

Conclusion

Gauge pressure and absolute pressure are both ways of measuring pressure, but they are different in definition and measurement methods. In actual production work, only by understanding the difference between gauge pressure and absolute pressure can we choose the appropriate pressure type to measure according to the actual working conditions. This is of great significance to ensure the stability and reliability of the production process and the accuracy of the measurement data.

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