What is Gauge Pressure, and How Do We Measure it?

What is Gauge Pressure, and How Do We Measure it?

If you’ve ever been curious about the term “gauge pressure,” you’re not alone. It’s a term used in many industries, but unless you’re a pressure gauge enthusiast, you might not have encountered it before. In this blog post, we’ll break down what a pressure gauge is, how it’s measured, and some of the instruments used to do so. Let’s dive right in, shall we?

What is Gauge Pressure?

Gauge pressure is the pressure of a substance, such as gas or liquid, relative to the pressure of the surrounding atmosphere. It’s essentially the difference between the pressure inside a vessel and the pressure outside of it. For example, if the pressure inside a tire is 35 PSI (pounds per square inch) and the atmospheric pressure is 14.7 PSI, the gauge pressure would be 20.3 PSI (35 – 14.7 = 20.3).

Gauge pressure is used in many industries, including but not limited to, manufacturing, oil and gas, and aviation. It’s an important measurement for ensuring the safe and efficient operation of equipment and processes.

How is Gauge Pressure Measured?

So, how do we measure this pressure? Well, there are a few ways, but let’s focus on the most common one: the good old pressure gauge. This little guy looks like a clock, but instead of telling time, it tells you the pressure in pounds per square inch (PSI). And no, it doesn’t have little hands that move around, but it does have a needle that goes up and down.

To use a pressure gauge, you need to connect it to the pipe or container you want to measure. You do this by using a fitting that screws onto the pipe or container and has a hole for the gauge to screw into. Once you have it connected, you can start measuring the pressure.

And how do you read the gauge? Well, that’s very easy.  Just look at where the needle is pointing. If it’s pointing to the left, that means the pressure is low. If it’s pointing to the right, that means the pressure is high. And if it’s pointing straight up, that means the pressure is just right.

However, be careful not to confuse gauge pressure with absolute pressure. Absolute pressure takes into account the atmospheric pressure around us, while gauge pressure only measures the pressure inside the container or pipe.

Types of Pressure Gauges

There are many different types of pressure gauges available, each with its own unique set of features and benefits. Here are a few of the most common types:

  • Bourdon tube gauges. These gauges use a curved tube that expands and contracts as pressure changes. The movement of the tube is then translated into a readable output. Bourdon tube gauges are commonly used in industrial applications and can measure a wide range of pressures.
  • Diaphragm gauges. These gauges use a flexible diaphragm that deforms as pressure changes. The deformation of the diaphragm is then measured and translated into a readable output. Diaphragm gauges are commonly used in applications where the pressure being measured is relatively low, such as in medical equipment.
  • Piston gauges. These gauges use a piston that moves as pressure changes. The movement of the piston is then measured and translated into a readable output. Piston gauges are highly accurate but are also more expensive and complex than other types of gauges.

Pressure Gauge Calibration

Pressure gauge calibration it’s like giving your pressure gauge a check-up to make sure it’s reading pressure correctly. And doing it is very simple.

The first step to calibrating your pressure gauge is to get a calibration device. This can be something like a deadweight tester or a pressure comparator. Don’t worry, these sound complicated, but they’re just fancy machines that help you check your gauge’s accuracy.

Once you have your calibration device, it’s time to get down to business. First, you need to compare the pressure gauge’s readings to the readings on the calibration device. If they match up, congrats, your gauge is accurate! If not, don’t panic, we can fix this.

Now, it’s time to adjust your pressure gauge, so it reads the correct pressure. This involves turning a little screw on the back of the gauge to either increase or decrease the reading. It’s like tuning a guitar but for pressure.

Once you’ve made the necessary adjustments, it’s time to check the gauge’s accuracy again. This might involve repeating the process a few times until you get it just right. Once you do it, your pressure gauge is now calibrated and ready to go. It’s like giving it a spa day and a new outfit all in one. Just make sure to check it regularly to make sure it’s still reading pressure accurately.

Factors That Affect Gauge Pressure

Now, let’s talk about the factor that can affect gauge pressure. The first one it’s temperature. Just like how hot chocolate can burn your tongue, the temperature can affect pressure too. When things heat up, the molecules inside the container or pipe start moving faster, causing the pressure to increase. So, if you’re measuring pressure in a hot environment, make sure to take temperature into account.

Next up, we’ve got altitude. Just like how it’s harder to breathe at high altitudes, pressure can be affected too. The higher you go, the less atmospheric pressure there is, which means the pressure inside containers and pipes will be lowered too. So, if you’re measuring pressure in the mountains, make sure to adjust for altitude.

Third on the list is the type of fluid you’re dealing with. Different fluids have different densities and viscosities, which can affect pressure. Think of it like trying to suck a thick milkshake through a straw versus a thin smoothie. The thicker the fluid, the harder it is to move, which can affect pressure readings.

And last but not least, we’ve got blockages. Just like how a blocked sink can cause water pressure to drop, blockages in pipes and containers can affect pressure too. If there’s a blockage somewhere, the pressure on one side of the blockage will be higher than the other, which can give you inaccurate readings.

Using Gauge Pressure in Industry

Gauge pressure is an important measurement in many industries, as it can provide valuable information about the operation of equipment and processes. For example, in the oil and gas industry, gauge pressure can be used to measure the pressure of a well or pipeline, which can help to identify potential issues such as leaks or blockages.

Similarly, in manufacturing, gauge pressure can be used to monitor the pressure of a system or process, such as a hydraulic system or a steam boiler. By monitoring gauge pressure, operators can identify any deviations from normal operating conditions and take appropriate action to prevent equipment damage or downtime.


Remember, gauge pressure is simply the difference between the pressure in a container or pipe and the pressure in the surrounding atmosphere. And measuring it is as simple as using a gauge that’s designed to measure it. So next time you’re dealing with gauge pressure, don’t be intimidated. It’s just a matter of understanding the basics and being aware of the factors that can affect it.

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