The difference between gauge pressure and absolute pressure

Deciding whether you need to measure gauge pressure or absolute pressure is important. If you choose the wrong reference your measurements could be off by 1 bar which can be a significant error depending on the situation

Gauge pressure

Gauge pressure is the most commonly used pressure reference because it uses the atmospheric pressure as a base value and any type of chamber will equalize with the pressure in the atmosphere when vented. This means that it is not necessary to subtract the atmospheric pressure to measure the change in pressure, which makes it the natural reference point for the majority of processes and test procedures. Gauge pressure, also called effective pressure, is generally signified by barg and psig (or bare and psie).

Absolute pressure

Absolute pressure is less used as a pressure reference because it will always be referred to a perfect vacuum or zero pressure. That is why the applications where absolute pressure is used as a measurement are often more specialized. Absolute pressure is commonly signified by bara or psia.

When to measure what?

Generally, if you want to measure any type of pressure that is influenced by the pressure in the atmosphere you use gauge pressure as a reference to see the total pressure minus the atmospheric pressure. This is used for example to measure the output of pressure of air compressors. If you want to measure pressures that are not influenced by the atmospheric pressure you use absolute pressure as a reference. An example would be leak testing a sturdy and completely sealed container. The difference between bar gauge and bar absolute is always equal to the atmospheric pressure.

Understanding Gauge Pressure in Saudi Arabia: Is 1 Bar Equal to Barg?

In Saudi Arabia's industrial sectors, accurate pressure measurements are crucial for the efficiency and safety of operations. Gauge pressure is a common metric used to measure the pressure relative to the ambient atmospheric pressure. Understanding the difference between gauge pressure and absolute pressure is essential when selecting and operating air compressors. Explore our range of compressors designed to meet your specific needs: Atlas Copco Compressors

Frequently Asked Questions

Is 1 bar equal to barg?

No, 1 bar is not equal to 1 barg. Bar is a unit of pressure that represents absolute pressure, including atmospheric pressure. Barg stands for "bar gauge" and measures pressure relative to atmospheric pressure. Therefore, 1 barg is equal to 1 bar above atmospheric pressure. At sea level, atmospheric pressure is approximately 1 bar, so 1 barg equals approximately 2 bar absolute pressure.

What is the difference between gauge pressure and absolute pressure?

Gauge Pressure (barg): Measures pressure relative to the ambient atmospheric pressure. It is the pressure reading you get when using most pressure gauges. Absolute Pressure (bara): Measures pressure relative to a perfect vacuum. It includes atmospheric pressure in its measurement. The relationship between them is: Absolute Pressure (bara) = Gauge Pressure (barg) + Atmospheric Pressure.