How Does an Aneroid Barometer Work?

Predictor Barometer

Barometers are weather instruments that measure changes in atmospheric pressure. While there are a few different types of barometers, Maximum specializes in aneroid barometers with the Proteus and Predictor models, as they are a safer way to measure atmospheric pressure than by using mercury and require no external power source, unlike digital barometers.

What is an Aneroid Barometer?

An aneroid barometer is a type of instrument used to measure atmospheric pressure. The name “aneroid” comes from the Greek words “a-” meaning ‘without’ and “nēros” meaning ‘liquid’. This name came about because all previous barometers used either mercury or water to measure changes in pressure. The invention of the aneroid barometer in 1844 by French scientist Lucien Vidi was a significant advancement from the traditional mercury barometer, as it is smaller, more portable, and more durable.

What Causes Air Pressure to Change?

The key factor behind air pressure changes is temperature. Warm air is lighter because its molecules move faster and are spread out. Cooler air is denser because its molecules move slower and are closer together.

So, when it’s warm, there’s lower air pressure because the air is lighter. When it’s cool, there’s higher air pressure because the air is denser.

How Do Aneroid Barometers Work Without Liquid?

They use a small metal box, known as an aneroid cell, which is designed to expand and contract with changes in atmospheric pressure. The aneroid cell consists of a thin, flexible metal capsule that is usually made of brass or an alloy of beryllium and copper. The cell has most of the air pumped out of it so that when the atmospheric pressure changes around it, the pressure inside the cell will also change, causing the capsule to expand or contract. To measure the expansion and contraction of the cell a mechanical linkage, including a spring, converts the movements of the capsule into the motion of a pointer on a dial, indicating the changes in atmospheric pressure.

The design of aneroid barometers is highly precise and requires meticulous calibration when manufactured to ensure accuracy. By adjusting the tension in the spring that connects the aneroid cell to the mechanical linkage, the barometer can be calibrated to provide highly accurate pressure readings for many years, as long as they are stored in a suitable environment. Because they are self-powered with nothing but mechanical parts, they can be serviced, will never experience any sort of power failure, and can be moved around throughout their lifespan from room to room or house to house.

Aneroid Barometer vs. Mercury Barometer

Aneroid and mercury barometers have a lot in common in that they are both used to measure atmospheric pressure, they’re both centuries-old technology, and neither require external power. However, there are several key differences between the two. Mercury barometers use a vertical glass tube which contains the mercury, and changes in the pressure cause the mercury to rise and fall within the tube, which is marked to indicate the corresponding atmospheric pressure.

Safety & Stability

The most important difference between the two types of barometers is simply that mercury is a hazardous material that is highly toxic, so if a mercury barometer ever starts to leak or the glass tube breaks there is a severe environmental risk. By contrast, an aneroid barometer uses nothing but metal and mechanical components, so there is no potential danger or risk associated with them. This is also why very few mercury barometers are still manufactured in the world, and most available are antiques.

Portability & Durability

One of the key advantages of aneroid barometers is their portability. Due to being self-powered as well as their small size and lack of liquid, they are easy to transport and can be used in various locations. Because the mechanism is all mechanical and has no glass components, they are also less likely to break than a mercury barometer. This makes them popular among meteorologists, hikers, pilots, and other outdoor enthusiasts who need to monitor atmospheric pressure while on the move. Mercury barometers are typically larger, heavier, and of course pose the risk of breaking and leaking when they are moved.


Aneroid barometers are a versatile and reliable way to measure atmospheric pressure. The design, which eliminates the need for liquid, makes them durable, portable and easily serviced or calibrated. With their ability to provide accurate and real-time pressure readings, aneroid barometers continue to play a crucial role in understanding and predicting changes in the atmosphere and are used by meteorologists worldwide. To learn more about atmospheric pressure and barometers, explore all of our articles and videos on the subject here, or feel free to contact us with any questions.

A barometer is the key to measuring changes in air pressure and predicting future weather. Browse our range of products.

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