How to measure atmospheric pressure

Even if we do not see it or perceive it, the air has weight and exerts a pressure. As it is a gas, it does so to all sides, since it tends to expand and this pressure is higher at sea level and decreases as one ascends in height. If you want to know how to measure atmospheric pressure, we explain it in the following article.

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The first mercury barometer was devised in 1643 by Evangelista Torricelli (1608-1647). It was a 76 cm glass tube filled with mercury and in turn deposited inverted in a tank filled with this element. Variations in atmospheric pressure create a larger or smaller vacuum column, causing the height of the mercury to vary within the tube and accurate measurements can be made.

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Another more convenient alternative for measurement is the aneroid barometer, which contains sealed cells that are compressed or expanded as a function of atmospheric pressure conditions. It is easier to transport and interpret than the traditional mercury barometer.

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Another instrument is derived from the aneroid barometer, which is dedicated to recording variations in atmospheric pressure over time: the barograph . With an inked needle on a roll of paper or aluminum rolled to a drum, in the manner of a seismograph, the different measurements made are constantly marked.

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Currently the mechanical means have been practically relegated as museum pieces or for purely didactic purposes, in favor of electronic and computer media that allow a more accurate reliability, as occurs with weather stations that allow to make a weather forecast, according to the atmospheric pressure conditions. High pressures mean good weather and stability, while low pressures are associated with meteorological instability and storms.

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The units of measure of the pressure are several. Thus, we can find the inches of mercury (inches Hg), the pascal (used by the International System of Units), the pounds per square inch (psi) of the English system or the torricelli (equivalent to 1 mm of mercury), among others .

In a common way we hear about the pressure measured in atmospheres and in bars and millibars, especially in the maps pressures of meteorological information. 1 atmosphere is equivalent, at sea level and 0ºC of temperature, to 101, 325 pascal, 1, 013.25 millibars, 1, 01325 bar 7 760 torricellis.