Tool to measure air pressure
For atmospheric pressure measurements a mercury barometer is used. It is a device in the shape of a closed tube of mercury-filled tube on one side. A vacuum is above mercury. Atmospheric pressure acting on mercury through the open end of the tube causes it to move up or down, resulting in a change in mercury column height. Mercury is also expanding under the influence of heat, so at different temperatures the same pressure will correspond to the different height of mercury. Therefore, all atmospheric pressure readings are reduced to air temperature 0 ° C using panels. Because of the different values of gravitational force, acting on mercury in different latitudes, barometer readings were also reduced to 45 ° geographic resonance. Pressure changes register aneroid. The main part of this device is a flexible metal can in which there is air. Under the influence of atmospheric pressure changes it deforms.
What instrument is used to measure air pressure?
For barometric pressure testing we use a barometer – a simple device. Nowadays known barometers operate on the basis of different principles, however, two basic groups of these devices stand out: liquid and spring barometers.
A liquid barometer is a device in which mercury is used. It is the only metal known to us, which is in the form of liquid. It is used in barometers due to, inter alia, high specific gravity. It is much larger than the weight of water. The second reason for using mercury in liquid barometers is that it does not lose its characteristic properties even at minus 36 degrees Celsius. This makes it possible to measure atmospheric pressure even in severe frosts. Torricelli’s barometer has undergone many changes. One of its variations is the Fortina barometer. Its name comes from the name of its constructor: Jean Fortin.
Aneroid or spring barometer
In meteorological stations, a spring barometer is much more often used for atmospheric pressure measurements. Lucien Vidie constructed it. This type of barometer is also called aneroid. It has a very simple construction. It is simply a metal, tightly closed can, in which there is no air. When the pressure increases, the can body shrinks. If the pressure drops, it will expand. Very simple construction makes aneroids extremely cheap. The advantage of aneroids is the very high accuracy of measurements.
Both liquid barometers (slowly coming out of use) and spring-loaded devices are very simple, cheap and extremely accurate. They can be used wherever atmospheric pressure is required.