There are different ways to measure pressure, which is defined as the force applied to an object or area. Two of the most common pressure measurements are gauge and absolute, but there is often confusion regarding the difference between the two.
Gauge Pressure (PSIG) 
Gauge pressure is the difference between absolute pressure and atmospheric pressure.
-
If the gauge pressure is above atmospheric pressure, it is positive.
-
If the gauge pressure is below atmospheric pressure, it is negative (vacuum).
Since gauge pressure readings are relative to the surrounding atmosphere, they can vary depending on the weather and elevation (sea level). If you are measuring pressure in an environment that is not significantly affected by atmospheric changes, you can measure in pounds per square inch gauge (PSIG).
Absolute Pressure (PSIA)
Absolute Pressure (PSIA)Absolute pressure is the sum of gauge pressure plus atmospheric pressure. A zero absolute pressure reading can only be achieved in a perfect vacuum and occurs naturally only in outer space.
If you need to measure pressure in an environment where atmospheric pressure changes constantly, you should measure in pounds per square inch absolute (PSIA). One of the most common uses for absolute pressure measurements is understanding and predicting weather patterns. These measurements are also vital in food packaging, aeronautical equipment, and gas analysis systems.
Conclusion
The fundamental difference between gauge and absolute pressure lies in how atmospheric pressure is factored into the measurement.
-
Gauge pressure measures the delta between a system’s internal pressure and the ambient atmospheric pressure—which varies by altitude and weather—and is typically recorded in PSIG.
-
Absolute pressure includes atmospheric pressure and is crucial for applications where atmospheric conditions fluctuate, such as meteorology, food preservation, and aviation; it is measured in PSIA.
Understanding this distinction is essential for selecting the correct measurement method for specific industrial applications.
Tools for Measuring Pressure
Measuring pressure incorrectly can lead to significant data errors, making it essential to use the right equipment. Whether your industry requires gauge or absolute pressure monitoring, MadgeTech offers a variety of data loggers for both PSIA and PSIG.
The PR1000 data logger, featuring an NPT fitting, is a prime example. The PR1000 is: 
-
Compact and submersible.
-
Available in 10 different ranges from 30 to 5000 PSI.
To learn more about the benefits of MadgeTech data loggers, please contact us.
sales@logicbus.com | support@logicbus.com | +1 619 616 7350 | Start conversation