What is a pressure gauge?

A pressure gauge is an instrument for measuring the condition of a fluid (liquid or gas) that is specified by the force that the fluid would exert, when at rest, on a unit area, such as pounds per square inch or newtons per square centimeter.

A pressure gauge is a fluid intensity measurement device. Pressure gauges are required for the set-up and tuning of fluid power machines and are indispensable in troubleshooting them. Without pressure gauges, fluid power systems would be both unpredictable and unreliable. Gauges help to ensure there are no leaks or pressure changes that could affect the operating condition of the hydraulic system.

The major functions of pressure gauges are to measure pressure in a fluid system. Pressure gauges have been employed in fluid power systems for almost a century, therefore it’s not surprising that pressure gauge designs are still evolving. Pressure gauges for fluid power applications have evolved over time to include more application-specific characteristics. 

For example, to prevent system leaks, pressure gauges are increasingly being developed with hydraulic-friendly pressure connections (such as SAE/Metric straight threads). Digital pressure gauges with customizable software allow process measurement of pressure-based leaks or other parameters such as torque, load, force, and hardness. Analog gauges with custom scales are more prevalent.

Applications

The followings are the applications of pressure gauges according to the types:

Differential pressure gauges are used to monitor filtration, liquid level, and liquid flow in a variety of industries. They’re important in refineries, petrochemical and chemical factories, power plants, and clean rooms, among other places.

Gauge pressure measuring devices are the most common pressure measuring equipment in the industrial world, especially in the power, refinery, chemical, petrochemical, pharmaceutical, food, refrigeration, air-conditioning, and sanitation industries.

Absolute pressure gauges are used to monitor adiabatic saturation pressure by meteorologists and to perform distillation operations in the oil refining industry. They can also be used to measure the vapor pressure of liquids, vacuum reactors, check leakage in tanks and circuits, and measure the fall in pressure of distillation vacuum columns. Vacuum pumps and the food packaging sector both employ absolute pressure gauges. Atmospheric pressure is measured via barometers.

Gauges verify that there are no leaks or pressure variations that could damage the hydraulic system’s operation.

Diagram of a pressure gauge:

Types of Pressure Gauge

The various types of pressure gauges are classified according to the following:

• Absolute pressure gauge

• Gauge pressure measuring device

• Differential pressure gauge

Absolute Pressure Gauge:

Absolute pressure is determined by comparing it to the pressure in a complete vacuum. In a complete vacuum, there is no pressure. As a result, it is referred to as ‘absolute’ pressure.

A measuring cell separated by a diaphragm makes up a conventional mechanical absolute pressure gauge. The reference chamber, which is a vacuum, is one part of the device. Absolute pressure can also be measured with a barometer, which is a hydrostatic gauge.

Gauge Pressure Measuring Device:

The gauge pressure is calculated using the standard atmospheric pressure at sea level as a reference (approximately 1013.25 mbar). When gauge pressure exceeds air pressure, it is positive; when it falls below atmospheric pressure, it is negative.

A Bourdon tube pressure gauge is the most popular device for measuring gauge pressure. It’s a mechanical device that’s made up of a C-shaped tube that’s sealed at one end. According to the applied pressure within the tube, which enters from the open end, the sealed end is free to move a pointer along a scale. Other mechanical devices that may measure gauge pressure include diaphragms and bellows. The u-tube manometer is effective among hydrostatic ones.

Differential Pressure Gauge:

The difference between two pressure readings is measured as differential pressure. It provides no information about the pressure levels at the two particular places it compares.