A barometer is a basic scientific device used in meteorology to measure atmospheric pressure sometimes called barometric pressure.

The word Barometer was derived from a Greek word ‘‘baros’’ meaning weight and ‘‘metron’’ which means measure. Atmospheric pressure is a tool to forecast weather, changes in the atmosphere which includes the air pressure.  Under most conditions, barometer can predict the weather for the 12 to 24 hours ahead so basically, Meteorologists use it in predicting short-term changes in the weather.  Old barometers contain a liquid in a glass with a reservoir at the bottom; the liquid can be mercury or water. The barometer tubes usually have makers which can be used to read the changes.

This scientific instrument measures atmospheric pressure in units of measurement which is called atmosphere or bars. Atmosphere (atm) is a unit of measurement equal to the average air pressure at a temperature of 150C (590 Fahrenheit).  Various barometers have been invented and used over the years. Evangelista Torricelli, an Italian physicist was credited with the inventing of first publicized the working barometer in 1643, though historical documentation suggests that an Italian Mathematician and Astronomer, Gasparo Berti unintentionally built a water barometer in the 1640 and 1643.

Types of Barometer

Mercury Barometer

A mercury barometer is the oldest type of barometer. It has a glass tube that is closed at the top and opens at the bottom with the mercury-filled reservoir. The weight of the mercury creates a vacuum in the top of the tube which is referred to as a Torricellian vacuum.  The mercury in the tube will adjust itself until the weight of the mercury column matches the atmospheric pressure exerted on the reservoir. When the pressure increases, it forces the mercury up the tube. Low pressure allows the mercury to drop to a lower level in the tube by lowering the force placed on the reservoir. The tube is always marked with a series of measurements that follows the number of atmospheres or bars.

Aneroid barometers

An aneroid barometer measures pressure without involving a liquid. It was invented by a French scientist, Lucien Vidi in 1844. Aneroid barometers use a sealed metal chamber made from an alloy of copper and beryllium which expands and contracts to depend on the atmospheric pressure around it. Mechanical levers measure the chambers expansion and contraction. Aneroid barometers are used in barographs and as radiosondes. They are commonly found in homes and small aircraft and also in recreational boats. The aneroid barometer is cheap, easy to use, and easy to transport as it has no liquid that could spill.

Digital Barometers

Digital barometers measure complex atmospheric data quickly and more accurately. They are used in other atmospheric readings like winds and humidity in accurately forecasting the weather. It also helps in making accurate elevation reading and also helps smartphone’s GPS receiver for tracking a location.


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