Tip 1: How to use the barometer

Tip 1: How to use the barometer

A barometer is a device for measuringatmospheric pressure. The main part of most barometers is a sealed box filled with gas. It is called an aneroid. To use the device is very simple, it is enough to look where its arrow points.

How to use the barometer

Kinds of barometers, the principle of their action

Barometers can be aneroid and mercury. The word "aneroid" means "without fluid". The principle of operation of such a barometer is quite simple: changes in atmospheric pressure lead to a change in the geometric dimensions of the aneroid, as a result, the arrow on the scale moves. Such barometers do not contain any dangerous elements, so they are suitable for use at home, in the conditions of a hiking trip. In addition to aneroid, there are mercury devices in which mercury is used to measure atmospheric pressure. Under the influence of atmospheric pressure, the height of the mercury column changes. The readings of these barometers are more accurate, just such instruments are used at meteorological stations. Mercury and its vapors pose a danger to humans, therefore, such devices are not used at home. Electronic meteorological instruments can be found on sale, as a rule, they are part of home meteorological stations. Such complex instruments also measure a number of other variables (for example, air temperature and humidity) and allow us to accurately predict the weather for the near future. Digital devices are less sensitive to shaking, so they are good for use in sea travel.

Using a barometer

It is not difficult to use an aneroid barometer. It is necessary to look at the value indicated by the arrow of the device. On the scale of the barometer, there are zones that are designated as "dry land", "clear", "variable", "rain", "storm", and also division with the indication of absolute values. If the pressure decreases - precipitation is expected, if it increases - it will be clear. As a rule, the barometer has two arrows - one movable, it is connected with an aneroid box, and the second one can be rotated. If it is combined with an arrow showing the magnitude of the atmospheric pressure, after a while you can observe which direction the movable arrow will move. Normal is the atmospheric pressure of 760 mm Hg. Art. at an air temperature of 15 ° C at the so-called sea level. Home barometers can measure its value in the range of 700-800 mm Hg. Art. at a height of not more than 300 m above sea level. A drop in pressure means worsening of weather conditions, approaching rain or snowfall. Zones with low pressure are called cyclones. Anti-cyclones are zones with increased pressure, their approach means the arrival of good weather. The barometer is adjusted if its readings differ from the readings of the local weather station by more than 8 mm Hg. Art. For this purpose, the adjusting screw located in the rear of the housing is provided. When setting, rotate it to an angle of no more than 45 degrees.

Tip 2: How to determine atmospheric pressure

Surely almost every day when you lookor listen to the weather forecast, then pay attention only to the air temperature and possible precipitation. But weather forecasters mention several more important parameters and atmospheric pressure among them. In general, atmospheric pressure is the pressure of the atmosphere on the earth's surface and all objects on it. A pressure acts on the human body, which is equivalent to the pressure of a 15-ton load. But we do not feel it, because there is air in our body too.

How to determine atmospheric pressure

You will need

  • a mercury barometer or an aneroid barometer. And if you need to continuously take pressure readings, then you should use a barograph.



Mercury barometer, as a rule, showsatmospheric pressure in millimeters of mercury. Just look at the scale of the mercury level in the flask - and now you know the atmospheric pressure in your room. As a rule, this value is 760 ± 20 mm Hg. If you want to know the pressure in pascals, then use a simple translation system: 1 mm Hg. = 133.3 Pa. For example, 760 mm Hg. = 133.3 * 760 Pa = 101308 Pa. This pressure is considered normal at sea level at 15 ° C.


Remove pressure readings from the barograph scaleis also very simple. This device is based on the action of the aneroid box, which reacts to changes in air pressure. If the pressure rises - the walls of this box bend inwards, if the pressure decreases - the walls straighten. The whole system is connected to the arrow, and you just need to see what value of the atmospheric pressure the arrow shows on the scale of the device. Do not panic if the scale is in such units as hPa - this is a hectopascal: 1 hPa = 100 Pa. And to translate into more familiar mm.rt.st. just use the equality from the previous paragraph.


And to find the atmospheric pressure on somea certain height can even be done without using the device, if you know the pressure at sea level. Only some mathematical skills will be required. Use this formula: P = P0 * e ^ (- Mgh / RT). In this formula: P is the required pressure at height h, P0 is the pressure at sea level in pascals, M is the molar mass of air equal to 0.029 kg / m, g is the ground acceleration of gravity, approximately equal to 9.81 m / s², R is the universal gas constant, is taken as 8.31 J / mol K, T is the air temperature in Kelvin (for the conversion from ° C to K, use the formula T = t + 273, where t is the temperature ° C), h is the altitude above where we find the pressure, measured in meters.