Aneroid barometer

You have surely heard that many of the meteorological phenomena have to do with changes in the atmospheric pressure. To be able to measure this atmospheric pressure, the barometer. It is a device capable of measuring what pressure the air exerts at all times. Thanks to the barometer, you can work on the weather forecast to be closer to what is going to happen with a smaller margin of error.

In this article we are going to show you how to use the barometer, how it measures atmospheric pressure and what it is for.

What is atmospheric pressure

Atmospheric pressure

Let's first do a quick reminder of what atmospheric pressure is. It is the force that the air exerts on the Earth per unit area. It could be said so that we easily understand what the column of air that we have over our heads would weigh. The weight exerted by air is what we call atmospheric pressure.

This pressure changes depending on many other variables such as temperature, humidity or the amount of solar radiation that affects us on the surface. In order to measure this atmospheric pressure we use the barometer. It is an instrument that allows us to measure it in units of mmHg or HPa. Normally, we place atmospheric pressure as a normal value at sea level. On this surface it has a value of 1013hPa. From this value, everything that is higher will be considered as high pressures and everything that is lower as low pressures.

Pressure decreases with height normally. The higher we climb in altitude, the less pressure we have and the less force the air exerts on us. The normal thing is that it decreases at a rate of 1 mmHg every 10 meters of height.

What is a barometer


Once we have reviewed how atmospheric pressure works, we are going to explain what the barometer is and how it works. The first was invented by a physicist and mathematician named Torricelli in the year 1643. Since then, there has been an interest in knowing the values ​​of the meteorological variables that affect our day to day. Its construction was of mercury and consisted of an inverted cylindrical tube that is open at the bottom and closed at the top. This tube was located on a reservoir that contained mercury.

The tube acted like a column of mercury, making the top empty. Therefore, the reading was interpreted as the height of the column inside the tube and was measured in mm. That's where the mmHg measurement comes from.

The second model of barometer that was invented is the best known and is the aneroid. It is formed by an interior metal box where the absolute vacuum has been made. The variations in atmospheric pressure are responsible for deforming the walls of the box and the variation is transmitted to a needle that indicates the values. There are double cameras and they are more accurate.

In meteorological observatories the barograph is used. It is a variant of this aneroid barometer, but it prints all the data on a graph paper. These values ​​are saved in a graph with all the data. It is very sensitive and capable of keeping pressure lines in 24/7 periods.

How to use the barometer

Torricelli barometer

To use barometers, especially the aneroid, you must first calibrate. It is recommended that they be calibrated right in the place where we are going to install it. As mentioned before, atmospheric pressure varies as a function of height and other variables. Ideally, therefore, calibrate it right at the place of use.

The calibration is made from a screw that we find in the back of the barometer and a screw tornavis. It is turned little by little to the left or right to calibrate it. It is recommended that we do the calibration in anticyclone periods where the pressure values ​​are more stable. This is important so that the data is more reliable and we have good measurements from the beginning.

For this calibration the reference values ​​established at sea level are taken. If we want to set the barometer in a city where it is at a certain height, we must do several things. The first is to maintain the total range of pressures that the instrument will show us at all times depending on the pressure at which we are. It is not the same to be in a coastal city than in the highest town in Spain.

Another option we have is to reduce the pressure at sea level to regulate the needle on the back of the barometer. We must always use the values ​​established by the official weather station.

Study of meteorological phenomena

Anticyclone and squall

Thanks to this measuring instrument we can know and predict some important pressure changes such as anticyclones and storms. Isobar maps are those that are made from collected atmospheric pressure data. The isobar is a curved line that joins the points where we are at the same pressure. If these lines are close together, it means that there are atmospheric pressure changes associated with a storm. On the contrary, if we have widely separated lines, we will have a stable situation thanks to the existence of an anticyclone.

High pressure systems are associated with stable and sunny weather with good environmental conditions in the surroundings. Thanks to these conditions, clouds cannot form nor can they have a vertical development.

Low pressure systems are those with low pressure air at their center. It is usually synonymous with rain, showers and strong wind. This is because air rises favor the growth and formation of clouds. Many of these clouds end up forming with vertical development until giving rise to precipitations. This is associated with bad weather.

I hope that with this information you will know more about the barometer and everything related to this instrument.

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  1.   Luis ac said

    VERY GOOD INFORMATION, quite synthesized, clear and simple to understand well ... CONGRATULATIONS! Maybe they should have added some more graphics, since this resource HELPS to better understand ...