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Uses of Barometers

10/8/2012 12:58:39 PM | by Anonymous


Barometers are widely used scientific instruments applied in meteorology for measuring atmospheric pressure in order to be able to provide a weather forecast. Although the weather forecast provided by barometers may not be for long term, it can be very beneficial for planning tasks for the day that are affected by the weather. The air pressure refers to the weight of the air in the atmosphere and it is this value that a barometer measures. The atmospheric pressure is constantly changing due to moving weather systems, and therefore barometers together with other meteorological instruments are used to determine the weather at a particular instance. In today’s market, there are two types of barometers that are used widely worldwide, the mercury barometers which are widely available and very much reliable, and the aneroid barometer which do not use liquid to take measurements and is more user friendly.


Devised by Evangelista Torricelli in 1643, a typical mercury barometer would have a glass tube that is about 3 feet high and has one end sealed and the other opened, with the open end being submerged in a container called the reservoir that contains mercury. As the atmospheric pressure around the tube changes, the level of mercury in the protruding glass tube out of the reservoir container changes. As the tube has a vacuum in it, where there is no mercury present, the results are not affected by trapped air inside the tube. The mechanics of a barometer is that it works in accordance with the weight of the air outside. If the weight of the air outside the glass tube is more than the mercury inside the tube, the mercury in the glass tube would rise and vice versa if the weight of the air is lesser than the weight of the mercury. The change in the glass tube would continue to occur until the weight of the weight of the mercury in the glass tube is the same as the weight of the air outside. The reason why the mercury in the glass tube rises when the weight of the air is more than the weight of the mercury is because air is able to push down on the exposed mercury stored in the container, which then pushes the mercury up the tube. Therefore, the higher the mercury level in the tube, the greater the air pressure is.


With the invention of Torricelli’s barometer, aneroid barometers were soon developed which do not require a liquid to function. The make up of these instruments is a flexible metal accordion box which resembles a bellows and is partially squeezed to a medium pressure. If the air pressure was to rise, the bellows would contract due to the fact that the air inside them would take up lesser space. They are also often linked to a recording device which records the changes in pressure and forms a barograph for reading. Such barographs are considered basic instruments of modern meteorology.


When used in conjunction with thermometers, barometers can provide general weather predictions. Predicting the weather may be very tough as weather can be very complex. However, storms usually have a pattern which they follow as significant changes happen in the atmospheric pressures right before the storm. The barometer is able to take note of these changes and then determine the weather. Also, air pressure is affected by the location as well. For example, the air pressure at the tip of a mountain would not be the same as below sea level. Therefore, the readings taken off barometers are usually converted to relevant numerals in comparison to air pressures at sea level. This helps to provide accurate readings to the user.

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