No matter how the pressure is generated, it can be specified and measured in various ways, but it is mostly measured in PSI, i.e, Pounds per Square Inch. Pascal, which is equivalent to 0.01 millibars is the S.I unit of pressure. The force per unit area is what pressure is defined as. The outcome of the force applied to an area is dependent on how the force is applied. Pressure is also like temperature; it can be applied in either one direction or in all directions.
Let us take an example. If one walks on the snow with the snowshoes on, he will not sink in for a long time. But if he walks shoeless on the snow, there are chances that he might sink in. Why is it so? The force that is being exerted on the snow is alike in both the cases, with the shoes on or without the shoes, what differs here is the force per unit area. When the person is wearing the snowshoes, the pressure applied on the surface becomes less because the force is spread out over a greater area.
PSI vs PSIG
The main difference between PSI and PSIG is that PSI is the force applied on a surface with one square inch of area, whereas PSIG, i.e PSI Gauge is a measure of pressure that is relative to the atmospheric pressure.
Comparison Table Between PSI and PSIG
| Parameter of Comparison | PSI | PSIG |
|---|---|---|
| Full form | PSI stands for Pounds per Square Inch. | PSIG stands for Pounds per Square Inch Gauge. |
| Meaning | PSI is the force applied on a surface with one square inch of area. | PSI Gauge is a measure of pressure, but a gauge measure only. |
| Application | It is mostly used in wastewater management, fuel storage and distribution, tire pressure, and so on. | It is mostly used in the refrigeration and air conditioning industry. |
| Calculation | PSI can be changed to various numbers of units that are used to measure pressure. | PSIG specifies that pressure is a measure relative to the atmospheric pressure only. |
| Measure | It is a measure relative to a vacuum. | It is a measure relative to the atmospheric pressure. |
What is PSI?
PSI is all about pressure measurement. It is the most used unit to measure pressure. It stands for Pounds per Square Inch. It is the force applied on a surface with one square inch of area and is a measure that is relative to a vacuum. It is used mostly in the United States for industrial, commercial, and household equipment. Different units are used in other countries to measure pressure.
- 1 PSI is equivalent to 6,894.76 pascals. Pascal is a much smaller unit for measuring pressure.
- 1 PSI is equivalent to 51.7149 Torr, 2.03602 inHg, 0.0689476 Bar, 0.068046 atmospheres, 27.7076 inches of water column, and so on.
PSIG and PSIA are the two variations of PSI that are often used. PSI can be changed to various numbers of units that are used to measure pressure.
Application of Pounds per Square Inch- It is mostly used to measure industrial applications. For example, it is used in wastewater management, fuel storage and distribution, tire pressure, measurement activities, and so on.
What is PSIG?
PSIG is a measure of pressure, but a gauge measure only. It stands for Pounds per Square Inch Gauge. PSIG specifies that pressure is a measure relative to the atmospheric pressure only. The gauge pressure is put in when the atmospheric pressure is lesser than the pressure in the system, where atmospheric pressure is the pressure applied by the atmosphere’s weight.
A container that does not have any air particles, would be approximately -14.7 PSIG. 0 PSIG is always used to measure a surrounding air pressure and it does not take into consideration the present barometric pressure. It is because of this reason that the barometric pressure sensors are non-relative. It would be pointless if a gauge sensor would have been used to estimate the barometric pressure.
32 PSIG is the suggested pressure for the car tires. The temperature outside and the barometric pressure are some other factors that can influence the inflation of the tires.
Application of Pounds per Square Inch Gauge- It is mostly used in the refrigeration and air conditioning industry. It is also used to disregard the results of the weather changes and the changing altitude and depth. Gauge pressure is also measured in many industrial applications such as construction appliances, airplanes, trucks, and cars.
Main Differences Between PSI and PSIG
- PSI stands for Pounds per Square Inch, whereas PSIG stands for Pounds per Square Inch Gauge.
- PSI is a measure relative to a vacuum. On the other hand, PSIG is a measure relative to the atmospheric pressure.
- PSI is the force applied on a surface with one square inch of area and PSI Gauge is a measure of pressure, but a gauge measure only.
- PSI is mostly used in wastewater management, fuel storage, tire pressure and distribution, and so on, while PSIG is mostly used in the refrigeration and air conditioning industry.
- PSI can be changed to various numbers of units that are used to measure pressure. PSIG specifies that pressure is a measure relative to the atmospheric pressure only.
Conclusion
The quantity of force applied on any surface is known as pressure. There are many ways to measure pressure.
It is necessary to understand the concept of PSI and PSIG since, in today’s world, the measurement of pressure is an important part of everyone’s life. This can be made evident with the help of some examples. When you drive your car or ride your bicycle, you first ensure that the tiers of the car or bicycle are boosted to the appropriate PSI. All tools today have pressure gauges to help them monitor the operations.
Even careers require the use of pressure measurements. The careers of meteorologists, mechanical and civil engineers, pressure instrument technicians are few such examples.
References
- https://www.tandfonline.com/doi/abs/10.1080/05698196808972238
- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9642/96420I/The-PSIG-procedure-to-Persistent-Scatterer-Interferometry-PSI-using-X/10.1117/12.2194984.short