We explain what a barometer is, its invention, function and in what units it measures. Also, the characteristics of each type of barometer.
What is a barometer?
A barometer it is an instrument used to measure atmospheric pressure that is, the weight that the atmosphere exerts in a given place on the Earth’s surface. Let us remember that the atmosphere is a heterogeneous mass of gases that covers the planet, and therefore has perceptible physical properties, such as weight, and that decisively influence the climate.
It is a very common artifact in meteorology, whose first versions date back to the 17th century built by the Italian physicist and mathematician Evangelista Torricelli (1608-1647), a student of Galileo Galilei. The invention of the barometer occurred as a means of demonstrating the weight of air, at a time when it was thought that it did not exert any type of pressure on the Earth’s surface.
The first barometer consisted of a glass tube closed at its upper end and open at the lower end, which was filled with mercury and inverted over a container filled with the same liquid, allowing the mercury to join with that which was already in the container. This occurred at first, increasing the level of mercury in the container, but up to a certain point.
Thus the question arose as to what force prevented all of the mercury from leaving the tube and spilling from the container. Precisely, the pressure that the air exerts in the opposite direction. This is what we know as atmospheric pressure.
This interpretation of the barometer was confirmed by Blaise Pascal (1623-1662) himself, who took one of these devices to the top of a mountain and noted that, as there was less air above it, the instrument’s readings varied, and the mercury He descended much further in the tube than at lower altitudes.
From then on the mercury barometer was used throughout the world and allowed greater knowledge of the behavior of the atmosphere and its link with the climate and the weather condition. However, since 2007 these instruments have been replaced by more modern versions, given the proven toxicity of mercury for living beings in general.
See also: Pressure
What is a barometer for?
As we said before, the barometer is used specifically to measure atmospheric pressure, that is, to measure the weight of the air mass above our heads which can vary according to altitude and according to the energy levels in the atmosphere.
This, in turn, allowed a greater understanding of the atmospheric climate, by verifying the link between the variation of atmospheric pressure (especially its decrease) and unstable weather. So thanks to the barometer we can have short-term predictions of atmospheric climate and know that when pressure increases there will be stable conditions, while when it decreases there will be bad weather.
Of course, other factors and elements also take part in this type of predictions, which is why the barometer readings are usually combined with an anemometer, a hygrometer and other similar instruments.
The barometers are also used to measure the pressure of all types of gases which is why they can also be found in packed gases, such as oxygen tubes
Barometer units
The current units with which barometers measure atmospheric pressure are hectopascals (hPa), which are a multiple (x100) of Pascals the minimum unit of pressure accepted in the International System of Weights and Measures. One Pascal is equivalent to a force of 1 Newton on a surface of 1 square meter, normal to it.
However, mercury barometers were traditionally used, the measurement of which was given in torra unit that pays tribute to Evangelista Torricelli, and is equivalent to 1 millimeter of mercury (mmHg).
Types of barometers
There are several types of barometers, each with its own characteristics, as we will see below:
- Mercury barometer. This is the traditional model created by Torricelli, which consists of a glass tube 850 mm high, filled with mercury and placed on a container filled with the same substance. Its use is not recommended due to the possibility of mercury poisoning.
- Aneroid barometer. Devoid of mercury, the aneroid is a barometer invented in 1843 by the French physicist Lucien Vidie (1805-1866), which measures atmospheric pressure through the deformations it exerts on a metal box with very elastic walls, inside which there is a absolute vacuum. Larger than the mercury barometer, it was quite inaccurate, due to discrepancies in the elasticity of the materials.
- Fortin Barometer. A variation of the mercury barometer, incorporating the elements for a fixed level (a screw resting on the tip of a small ivory cone), keeping the torricellian tube suspended and then covering the whole in a brass box, with a slot to be able to observe the measurements.
- digital barometer. The modern variant that takes advantage of new computerization technologies, and that uses special sensors to accurately capture the pressure of the atmosphere.
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References
- “Barometer” on Wikipedia.
- “What is a barometer for?” on Netatmo.
- “What is a barometer for?” VERY Interesting.
- “The History of the Barometer (and How It Works)” (video) on TED-Ed.
- “Barometer” in The Encyclopaedia Britannica.
