How do you measure air pressure ?
In 1643, a scientist named Evangelista Torricelli of Italy proved that the air of the atmosphere exerts pressure. Normally the pressure of the atmosphere is about 7 kg. per square inch. He also made a simple barometer to measure the pressure of air. To make a simple barometer, fill a one meter long glass tube, whose one end is closed, with mercury and close its open end with the thumb and put it in a tub filled with mercury, then remove the thumb, So some of the mercury will come out of the tube and fall into the tub. As soon as the height of the mercury column is about 76 cm. When it reaches, it will stop falling in the tub. 76 cm. This column of mercury stops at a height because the air of the atmosphere exerts pressure on the surface of the mercury in the tub and does not allow it to fall down. This column of mercury tells the pressure of the atmosphere, if the area of the glass tube is one square inch, then the weight of this mercury in the tube is about 7 kg. Will happen. On this principle, a scientist named Fortin made an excellent type of barometer, which is called Fortin Barometer.
Two types of barometer are used to measure the pressure of the atmosphere. Mercury Barometer and Aneroid Barometer. Mercury barometers are made according to the above method. Fortin's forward barometer is a mercury barometer. It is usually hung on the wall in laboratories. Its size is quite big. Therefore, it is difficult to carry it from one place to another. Anhydrous barometers have been designed to get rid of this difficulty. No liquid is used in these.
Hypnotic barometer is a metal box, inside which the air is taken out. A diaphragm is mounted on it. It is related to a metal director by levers. A scale is attached to this instrument. As soon as there is a change in the future, so does the effect on the diaphragm. This effect is transmitted by the levers to the director and read on the pressure change scale (see picture above).
