When it comes to predicting weather patterns, measuring air pressure is an essential step. That’s where the barometer comes in – the trusty weather instrument that’s been used for centuries to track atmospheric changes.

In this article, we’ll take a closer look at the barometer and its role in weather forecasting. We’ll explore how this weather instrument works, its history, and the different types available. We’ll also discuss how to read a barometer, its various applications, and tips for proper maintenance.

What is air pressure?

Air pressure, also known as atmospheric pressure, is the force exerted by the weight of the air above us. It is measured using a barometer, which consists of a long tube filled with mercury or an aneroid cell that reacts to changes in air pressure.

As altitude increases, atmospheric pressure decreases. Therefore, barometers are used to measure altitude as well as weather patterns.

PascalPa1 Pa = 0.00001 atm
Atmosphereatm1 atm = 101325 Pa
Barbar1 bar = 100000 Pa

The most widely used unit of measurement is the bar, which is equal to 100,000 Pascals.

Types of barometers

There are two main types of barometers: mercury and aneroid.

Mercury BarometerAneroid Barometer
A glass tube filled with mercury is inverted into a dish of mercury. The pressure of the atmosphere pushes the mercury up the tube, creating a vacuum at the top. The height of the mercury column is directly proportional to the air pressure.A metal box is partially evacuated and sealed. A small, flexible metal capsule inside the box expands or contracts in response to changes in air pressure. The movements of the capsule are amplified by a system of levers and communicated to a pointer on a dial.

The mercury barometer is more accurate than the aneroid barometer, but it is also more fragile and difficult to transport. Mercury is also toxic and can be harmful if the barometer is mishandled.

The aneroid barometer is more portable and less expensive than the mercury barometer. It is also more durable and requires less maintenance. However, the aneroid barometer is less accurate than the mercury barometer and can be affected by changes in temperature and humidity.

History of barometers

Barometers have a long and interesting history, dating back to the 17th century. The invention of the barometer is credited to Evangelista Torricelli, an Italian physicist and mathematician, who in 1643 created the first barometer using a glass tube filled with mercury. The mercury barometer quickly became the standard instrument for measuring air pressure and remains in wide use today.

In the following years, improvements to the barometer were made by scientists such as Robert Boyle and Edmond Halley. Halley’s design for a portable barometer that could be used for navigation at sea was especially important for the maritime industry. By the 19th century, the aneroid barometer, which used a small, flexible metal box instead of a liquid, was developed. The aneroid barometer is now commonly used in homes and offices because it is more compact and less fragile than a mercury barometer.

Contributions to the development of barometers

In addition to Torricelli, Boyle, and Halley, other notable contributors to the development of barometers include Blaise Pascal, who first demonstrated the relationship between atmospheric pressure and altitude; Jean Picard, who developed a more accurate version of the mercury barometer; and Lucien Vidie, who invented the marine barometer, a type of aneroid barometer that was more resistant to moisture and temperature changes.

Today, barometers continue to be an essential tool for weather forecasting, aviation, and other fields where accurate air pressure readings are critical.

Other instruments that measure air pressure

Aside from the barometer, there are other instruments that can measure air pressure. These instruments are used in different fields and have their own unique features.


One such instrument is the altimeter, which measures air pressure to determine altitude. This is particularly useful in aviation, where pilots need accurate altitude readings to ensure safe flight. The altimeter works much like a barometer, but is calibrated to show altitude rather than atmospheric pressure.


Another instrument that measures air pressure is the hypsometer, which is used to determine the height of a mountain or other tall structure. The hypsometer works by comparing the boiling point of water at different altitudes, which changes with air pressure. This allows the instrument to calculate the height based on the difference in boiling points.

While these instruments have their own unique uses, the barometer remains the most versatile and widely used instrument for measuring air pressure.

How to read a barometer

Reading a barometer is a fairly simple process, but it does require some practice to accurately interpret the readings. Here are some steps to follow:

  1. First, make sure the barometer is calibrated and set to the local air pressure (see previous section for tips on calibration).
  2. Next, observe the position of the mercury or aneroid capsule in the barometer tube or dial.
  3. If the mercury level has risen, it indicates an increase in air pressure and clear, stable weather. If the mercury level has fallen, it indicates a decrease in air pressure and the possibility of stormy weather.
  4. For an aneroid barometer, the dial will typically have a needle that moves to indicate changes in air pressure. The same rules apply – a rising needle indicates high pressure and stable weather, while a falling needle indicates low pressure and the possibility of stormy weather.
  5. It’s important to note that the absolute reading of the barometer is less important than the trend – whether the pressure is rising or falling is a better indicator of what kind of weather to expect.

With regular use and practice, you’ll become more comfortable reading your barometer and interpreting its readings.

Applications of air pressure measurement

The measurement of air pressure has various applications in different fields, from weather forecasting to aviation and scuba diving. Accurate air pressure readings are critical for these activities, as they help provide valuable information for making informed decisions.

Weather ForecastingAir pressure measurements help meteorologists determine changes in weather patterns and predict potential weather events, such as thunderstorms or hurricanes.
AviationBarometers are used to measure air pressure at different altitudes, allowing pilots to determine their current altitude and make necessary adjustments to maintain a safe flight.
Scuba DivingScuba divers use dive computers that rely on air pressure measurements to calculate their depth and remaining dive time. Accurate readings are vital for ensuring a safe and enjoyable diving experience.

Without the ability to measure air pressure accurately, these activities would become significantly more dangerous and unpredictable. By monitoring changes in air pressure, we gain valuable insights into the world around us and can make informed decisions that keep us safe and prepared.

Maintenance and Care of Barometers

Proper maintenance and care of your barometer can help ensure accurate readings and prolong its lifespan. Here are some tips to keep in mind:

CleaningEvery 6 months
CalibrationEvery 3-6 months
StorageWhen not in use

Cleaning: Use a soft cloth or brush to remove any dust or debris from the barometer’s surface. Avoid using water or chemicals.

Calibration: Follow the manufacturer’s instructions for calibrating your barometer. This may involve adjusting the set screw or using a calibration tool. Test the instrument against a known standard to ensure accuracy.

Storage: When not in use, store your barometer in a cool, dry place away from direct sunlight. This will help prevent damage from temperature fluctuations and moisture.

If you encounter any issues with your barometer, such as inaccurate readings or mechanical problems, consult the manufacturer’s instructions or seek the advice of a professional technician. Taking care of your barometer can help ensure its reliability and accuracy for years to come.


If you’re new to using a barometer or have some questions about its usage, we’ve got you covered with the following frequently asked questions.

How do I interpret the readings on a barometer?

The readings on a barometer indicate atmospheric pressure in inches of mercury or millibars. Generally, a high reading indicates clear weather while a low reading can suggest the possibility of precipitation or other atmospheric disturbances.

How often should I calibrate my barometer?

It’s recommended to calibrate your barometer every six months to ensure accurate readings. However, if you notice significant changes in readings or suspect that the instrument has been damaged, calibration may be necessary sooner.

Are there any safety considerations when using a barometer?

Barometers are generally safe to use, but it’s important to ensure that the instrument is placed in a stable location and not subject to extreme temperatures or moisture. Additionally, be sure to handle the instrument carefully to avoid accidental damage or breakage.

Can I use a barometer for activities like hiking or camping?

While a barometer may be helpful in predicting weather patterns for outdoor activities, it’s important to note that it should not be relied upon as the sole source of information. Other weather forecasting tools and resources should also be consulted, and safety should always be the top priority when engaging in outdoor activities.