AS9120B, ISO 9001:2015, and FAA AC 0056B ACCREDITED

How Does a Pressure Gauge Work?

A pressure gauge is an instrument used to measure and monitor the pressure of fluids to make sure that the liquid or gas is at the desired pressure limit. When the pressure of a gas or liquid inside an instrument is too high, it can damage equipment or even cause an explosion, so it is vital to monitor pressure. Pressure gauges let off alarms when pressure levels exceed what they should be in order to alert the operator of the equipment. Operating aircraft requires monitoring pressure levels, such as those within the engine group and the flight group, for safe flights. Pressure measurements within aircraft depend on Bourdon tubes, diaphragms, and solid-state sensing devices.

How Pressure Gauges Measure and Report Pressure?

Pressure gauges work on the basis of Hooke’s law, which states that there is a direct and linear relationship between the force applied to extend or compress a spring and the distance the spring compresses or extends. When pressure increases on the inside of equipment, the spring compresses to produce a higher reading on the pressure meter display. Some pressure gauges are purely mechanical, though digital pressure gauges are common today because of their ability to directly produce readings on computers and smartphones. Digital pressure gauges rely on a switching circuit of AC to DC power. When pressure is measured in a digital pressure gauge, it is transmitted to a sensor diaphragm which determines the electrical signal to generate as a reading. This reading appears on a dial situated in the cockpit for the pilot, and with digital pressure gauges, it appears on a liquid crystal display (LCD).

Types of Pressure Gauges

There are many types of pressure gauges available on the market, so choosing the best design requires consideration. A few factors contribute to determining which type of gauge a plant needs, including the size of the application and the chemical components of the fluid being measured. A few common types of gauges are commercial gauges, general service gauges, stainless steel industrial pressure gauges, differential pressure gauges, and double-sided pressure gauges. Double-sided pressure gauges are very common, especially in chemical industries and oil & gas industries because they have many benefits and are highly reliable. These gauges are made with plastic bodies and can withstand high temperatures and corrosive or abrasive materials. On top of their durability, double-sided pressure gauges are highly reliable with alert mechanisms being present for when the filter must be replaced, and they come with a dual scale that allows the user to select between PSI/KPA and PSI/BAR measurement units. Unlike simple commercial pressure gauges, differential pressure gauges measure two different pressures from two separate chambers and monitor both with a piston attached to a spring that moves back and forth from the chamber of lesser pressure. These types of pressure gauges are used in cases where both chambers have the same desired pressure, and the differential would indicate some form of contamination on either side, such as in a filter.

Pressure Gauges for Aircraft

Within aircraft, the pilot relies mainly on differential pressure gauges for safe operations. This type of pressure gauge is best because it allows for accurate measurements of the high pressures that aircraft devices endure. The measurements are determined by solid-state pressure sensors and a Bourdon tube which holds and measures the fluid being monitored. This tube is attached either directly to the dial of the pressure gauge or to the pilot’s instrument panel. The Bourdon tube is often metal which makes it durable for temperature changes in flight. This type of design should be used in pressurized aircraft, for example, in the engine oil pressure gauge. It is important that the pilot can monitor pressure in the cockpit by reading and calibrating the measurements reported on the sensor attached to the pressure gauge.


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September 19, 2022
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