What is a barometer?This technical term is called a device for measuring atmospheric pressure.The most widely used two types of barometers.Mercury barometer used to measure atmospheric pressure, mainly on the meteorological stations.
It is more cumbersome, but also gives greater measurement accuracy, so scientists and give preference to him.The barometer of this type was invented and built by the Italian scientist Evangelista Torricelli in 1644.The principle of its action - balancing the mercury column with a column of air.Because of the high density of mercury column height is very low (when we say that atmospheric pressure - 760 millimeters of mercury, which means that with the same force pushes the air at the point of measurement).
aneroid barometer - a device more complex.Although the idea of the device was expressed almost simultaneously with the invention of the barometer of mercury (did it in the same seventeenth-century German scientist Gottfried Leibniz), but the practical implementation of the idea of the great German received only two hundred years.In 1847 the talented French engineer Lucien Vidi created the world's first aneroid.What is the principle of his actions?
Barometer was named "aneroid", that is anhydrous.This term is the creator wanted to emphasize that the device does not use any liquid, unlike the mercury barometer, where the sensor element is a liquid metal.
The aneroid sensing element is sealed box of corrugated material, which is increased or decreased air pressure slightly shrinks or expands.The system of levers actuates the arrow, which is specifically a graduated scale indicating the atmospheric pressure in millimeters of mercury.
It would seem, nothing complicated, and aneroid could be created at the level of technological development as the Torricelli times and before.Why did not it happen?Rather, here he played the role of a combination of several factors.First and foremost - is the lack of need for such an instrument at the time.In fact, meteorology as a science in its infancy, and the dependence of small variations in atmospheric pressure and the weather just was realized by scientists of the time.In addition, the possible role played by the lack of a suitable material for corrugated boxes (it must have an acceptable elasticity and stretch during continuous operation).With the development of science and the first and second conditions are no longer prevent the creation of aneroid.
After the invention Lyuena Vidi aneroid barometer began to spread rapidly in private houses and apartments.There was even a kind of fashion: the availability of this device in the house emphasized social and intellectual status of the host.Such a person, in modern parlance, considered "advanced".
With the adoption of an international metric system (SI), most countries graduated scale aneroid become complemented by the scale, where the pressure is not only indicated in millimeters of mercury (it is not a systemic one), but also in Pascal.There is a grading scale aneroid bars.Bar - also non-system unit, approximately equal to one atmosphere.Sometimes measure pressure in bar is more convenient than in millimeters of mercury, or in system units.
However, the habit of measuring the atmospheric pressure in millimeters of mercury has been very strong.Even in weather forecasts atmospheric pressure indicated in these non-system units.
