A barometer detects atmospheric pressure and is used for weather forecasting and height calculation. Know its different varieties, applications, and working.

What is a barometer?

A barometer is a scientific device used to detect air pressure in a specific environment. The pressure tendency can foretell short-term weather changes. Surface weather analysis makes extensive use of air pressure readings. Its purpose is to aid in detecting frontal borders, pressure systems, and surface troughs. It is scientific equipment used to measure atmospheric pressure, often known as barometric pressure.

Many layers of air surround the Earth in our atmosphere. As gravity draws it to Earth, this air has weight and presses on everything it comes into contact with. This pressure may be measured with a barometer.

A barometer measures and monitors atmospheric pressure in atmospheres or bars. At 15 degrees Celsius, one atmosphere (atm) at 59 degrees Fahrenheit is a unit of measurement equal to the average air pressure at sea level.

Because air density is lower at higher altitudes and exerts less pressure, the number of atmospheres decreases. The air density rises as height drops, as does the number of atmospheres. To get correct atmospheric pressure measurements, barometers must be adjusted for variations in height.

How does a barometer work?

The most basic barometer is a tall closed tube standing upside down in a mercury bath. This liquid rises partially up the tube, similar to a thermometer, to be measured. 

Mercury is used in barometers because it is more handy than water. That is because water is less thick than mercury. As a result, air pressure will raise a certain volume of water significantly higher up in the tube than the same volume of mercury. With water, it requires a fairly long tube, making that barometer impossible to use.

The Working Principle of Barometer

Evangelista Torricelli, an Italian mathematician, devised the Torricellian barometer. He used a lengthy glass tube that was sealed at one end and contained mercury. Then he placed his finger over the open end, tilted it upside down, and placed it upright in the mercury bowl. He was extremely cautious and did not allow any air into the tube. 

The space that would form above the mercury column was a vacuum. In fact, it was the first time a vacuum had been created in a laboratory. As a result, this form of vacuum was referred to as a Torricellian vacuum in honor of its originator.

At sea level, the atmosphere pushes down on the mercury, causing it to rise in the tube to around 760 mm. One atmosphere, or 1 atm, is the name given to this atmospheric pressure. For example, the pressure at the summit of Mount Everest is about one-third that of normal air pressure at sea level. It will be around 0.3 atm.

Types of the Barometer

There are two main types of barometers:

Mercury barometer

This is the most often used barometer. It is made up of a glass column with mercury and has inch marks. Its top end is sealed, while the bottom end is resting in a mercury cup, i.e., a cistern. These barometers are calibrated for gravity and ambient temperature to improve accuracy. Mercury is used for its density.

Aneroid barometer

This type of barometer is made of fluid. It is made up of the aneroid capsule, a thin and flexible metal box made of an alloy. This is a beryllium and copper alloy. The box is hermetically sealed to allow for greater contraction and expansion of the levers and springs caused by changes in air pressure outside the box.

Torricellian barometers are helpful and provide precise readings, but mercury is dangerous. Thus, many avoid it to keep it at home. As a result, most individuals who own barometers choose those with easy-to-read dials, such as aneroid barometers. The box either squashes inside or flexes outward when air pressure rises or falls. 

The spring is cleverly secured to the box. With the variations in air pressure, the box slides in and out. This spring stretches and contracts, causing the dial’s pointer to move. This dial has been calibrated to instantaneously read the air pressure.

What are the uses of a barometer?

A mercury barometer measures barometric pressure by using the physical characteristics of mercury in a tube.

  • atmospheric pressure measurement
  • determining a location’s height
  • Forecasting the weather
  • Aneroid barometer calibration and testing
  • Fluid mechanics application
  • Pressure measurement in aircrafts
  • Surface weather forecasting
  • Barograph preparation
  • Application in Physics, Astronomy, and Chemistry
  • Altimeter preparation for aircraft

What is the primary difference between manometers and barometers?

Both instruments – manometers and barometers – are helpful for measuring air pressure. The barometer is a closed-end manometer that is a little simpler than the usual manometer. Except for air pressure, we can’t measure other forms of pressure with a barometer. We can calculate pressures far lower than atmospheric pressure using a manometer. The manometer has two open ends, whereas the barometer has one end that is constantly shut and has a vacuum associated with it.


There was the barometer before there were applications that could forecast the weather with the tap of a finger. In the mid-17th century, an Italian scientist named Evangelista Torricelli wanted to develop a system for measuring air pressure. This gadget is named the barometer.

A barometer’s purpose is to tell if the atmospheric pressure increases or decreases. When it comes to studying the nature of storms and anticipating weather changes, they are vital tools for scientists and weather forecasters.