Barometer aneroid: household appliance for measuring atmospheric pressure

What is a barometer? This technical term is commonly called a device for measuring atmospheric pressure. Two types of barometers were most widely used. The mercury barometer is used to measure atmospheric pressure primarily at meteorological stations.
It is more cumbersome, but gives a greater accuracy of measurement, so scientists prefer it to him. A barometer of this type was invented and built by the Italian scientist Evangelista Torricelli in 1644. The principle of its operation is the balancing of the mercury column with the column of atmospheric air. Due to the high density of mercury, the height of the column is very small (when it is said that atmospheric pressure is 760 millimeters of mercury, this means that the atmospheric air at the measuring point presses with the same force).

The aneroid barometer is a more complex device. Although the idea of the device was expressed almost simultaneously with the invention of a mercury barometer (this was done in the same seventeenth century by the German scientist Gottfried Leibniz), but the practical embodiment of the idea of a great German was received only two hundred years later. In 1847, the talented French engineer Lucien Vidi created the world's first aneroid barometer. What is the principle of its operation?

The barometer was called an "aneroid," that is, anhydrous. By this term, the creator wanted to emphasize that the device does not use any liquid, in contrast to the mercury barometer, where the sensitive element is a liquid metal.
In the aneroid, the sensitive element is a sealed box of corrugated material, which, when the atmospheric pressure is raised or lowered, contracts slightly or expands. The system of levers drives the arrow, which on a specially graduated scale indicates atmospheric pressure in millimeters of mercury.

It would seem that nothing complicated, and the aneroid barometer could be created at the level of technology development both of Torricelli's time and before it. Why did not this happen? Most likely, a combination of several factors played a role here. The first and main thing is that there was no need for such an instrument at that time. In fact, meteorology as a science was just emerging, and the dependence of small variations in atmospheric pressure and weather was only realized by scientists of the time. In addition, perhaps, the absence of a suitable material for the corrugated box (it should have an acceptable elasticity and do not stretch during the long-term operation) played its role. With the development of science, both the first and second circumstances ceased to prevent the creation of an aneroid.

After the invention of Luyen Vidi, the aneroid barometer began to spread rapidly through private houses and apartments. There was even a peculiar fashion: the presence of this device in the house emphasized the social and intellectual status of the owner. Such a person, speaking in modern language, was considered "advanced".

As the international metric system (SI) was adopted by most countries, the graduation of the aneroid scale was supplemented by a scale where the pressure was indicated not only in millimeters of mercury (this is not a system unit), but also in pascals. There is also a graduation of the aneroid scale in bars. Bar - also a non-system unit, roughly equal to one atmosphere. Sometimes it is more convenient to measure pressure in bars than in millimeters of mercury or in system units.

However, the habit of measuring atmospheric pressure in millimeters of mercury was very strong. Even now in weather forecasts, atmospheric pressure is indicated in these non-systemic units.