What is a Barometer?

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A barometer is a device used to measure air pressure based on the weight of the air column. The barometer was invented by an Italian scientist Evangelista Torricelli, who studied the characteristics of mercury in a vacuum and developed the first barometer.

There are two main types of barometers, which include the most commonly used mercury barometers and the newer digital aneroid barometer.

Working Method

A typical barometer consists of a glass tube with opened and closed ends. The tube filled with mercury is fixed upside down in a reservoir containing mercury and a ruler is placed alongside the tube. A vacuum is created at the top when the mercury level in the glass tube falls.

The barometer is operated by balancing mercury weight in the glass tube over the weight of atmospheric pressure. The mercury level in the glass tube increases, if the weight of mercury is less than the atmospheric pressure. The mercury level decreases if the weight of mercury is greater than the atmospheric pressure.

However, the mercury level is subjected to change constantly till the weight of the mercury in the tube is equal to the weight of the air above the reservoir. The rising and falling of mercury level can be measured using the ruler, and thus recording the changes with time.


Barometers have been mainly used for measuring weather patterns. When barometers are used in combination with wind observations, they can provide considerably accurate short-term weather forecasts.

They are also used in measuring the speed of an aircraft by checking the pressure of air moving against aircraft. They also serve as altimeter settings indicators to provide altitude information to aircraft altimeters.

They also play a major role in improving the precision of missile and satellite tracking systems by calculating the humidity conditions which would hinder the travel of satellites and missiles.

References and Further Reading


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