A barometer is an instrument that measures atmospheric pressure. Atmospheric pressure is the weight per unit area exerted by the atmosphere.
GENERAL OPERATION
The first barometers were made up of a column of liquid enclosed in a tube whose top is closed. The weight of the liquid column exactly compensates for the weight of the atmosphere.
HISTORY OF THE BAROMETER
The first barometers were made by the Italian physicist and mathematician Evangelista Torricelli in the 17th century. Atmospheric pressure is equivalent to the height of a column of water about 10 m high. In mercury barometers, whose density is 13.6 times that of water, the column of mercury supported by atmospheric pressure at sea level on a clear day is approximately 760 mm. Barometers are essential instruments for measuring the state of the atmosphere and making weather forecasts. High pressures correspond to regions without precipitation, while low pressures are indicators of regions of storms and storms.
HYGROMETER
A hygrometer is an instrument used to measure the degree of humidity of the air, the soil, the plants, giving a quantitative indication of the environmental humidity.
The absorption hygrometer uses hygroscopic chemicals, which absorb and exhale moisture, depending on the surrounding circumstances.
The electric hygrometer is made up of two spirally wound electrodes between which is a fabric impregnated with aqueous lithium chloride. If an alternating voltage is applied to these electrodes, the tissue is heated and part of the water content evaporates. At a defined temperature, a balance is established between the evaporation by heating of the fabric and the absorption of water from the ambient humidity by lithium chloride, which is a very hygroscopic material. From these data, the degree of humidity is precisely established.
