The barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Trend pressure can predict short-term changes in weather. Many air pressure measurements are used in surface weather analysis to help find surface troughs, high pressure systems and frontal boundaries.
Barometers and pressure altimeters (the most basic and common altimeter types) are essentially the same instruments, but are used for different purposes. An altimeter is intended to be transported from one place to another to match the atmospheric pressure to the appropriate height, while the barometer remains stationary and measures the subtle changes caused by the weather. The main exception to this is the ship at sea, which can use a barometer because their elevation is unchanged.
Video Barometer
History
Although Evangelista Torricelli is universally credited with creating a barometer in 1643, historical documentation also shows Gasparo Berti, an Italian mathematician and astronomer, accidentally constructing a water barometer between 1640 and 1643. French scientist and philosopher RenÃÆ'Â Descartes describes the experimental design. to determine atmospheric pressure as early as 1631, but there is no evidence that he built a work barometer at that time.
On 27 July 1630, Giovanni Battista Baliani wrote a letter to Galileo Galilei describing an experiment he had made in which a siphon, which led to a hill about twenty-one meters high, failed to function. Galileo replied with an explanation of the phenomenon: he proposed that it was the power of a vacuum that held water, and at a certain height the amount of water became too much and the force could not hold back, like a cable that could support so much weight. This is a re-statement of horror vacui theory ("nature hates the emptiness"), which comes from Aristotle, and which Galileo repeated as resistant vacuo .
Galileo's idea reached Rome in December 1638 in his book Discorsi . Raffaele Magiotti and Gasparo Berti were excited by these ideas, and decided to find a better way to try to produce a vacuum than with siphon. Magiotti designed such experiments, and sometimes between 1639 and 1641, Berti (with Magiotti, Athanasius Kircher and NiccolÃÆ'² Zucchi present) carrying them out.
Four Berti experimental accounts exist, but the simple model of his experiment consists of filling with long tube waters with both ends attached, then standing tubes in a water-filled basin. The lower end of the tube is opened, and the water inside it flows into the basin. However, only a portion of the water in the tube is flowing out, and the water level inside the tube remains at the right level, which is incidentally 10.3 m (34Ã, ft), the same height as Baliani and Galileo has observed that it is limited by siphon. What is most important of these experiments is that the thinning water has left a space above it in a tube that has no contact between with the air to fill it. This seems to suggest the possibility of a vacuum in the space above the water.
Torricelli, friend and disciple of Galileo, interpreted the experimental results in a new way. He proposes that the atmospheric weight, not the vacuum appeal, holds water in the tube. In a letter to Michelangelo Ricci in 1644 on experiments, he wrote:
Many say that empty space does not exist, nothing is empty, regardless of natural disgust and with difficulty; I know nobody says that it exists without difficulty and without resistance from nature. I think so: If anyone can find the real cause of where resistance can be derived that is felt if we try to create a vacuum, it seems I am stupid to try attributes to vacuum operations that follow clearly from some other cause. ; and by making some very easy calculations, I find that the cause given by me (ie, the atmospheric weight) should be by itself only to offer greater resilience than when we try to generate a vacuum.
It is traditionally considered (mainly by Aristotle) ​​that air has no lateral weight: that is, that the air miles above the surface do not give weight to the body beneath it. Even Galileo has received air without weight as a simple truth. Torricelli questioned the assumption, and instead proposed that the air had weight and that it was the last (not the exciting power of the vacuum) held (or rather, pushed) up into the water column. He thinks that the water level living in (10.3 m) is reflecting the heavy strength of air pushing on it (in particular, pushing water in the basin and thus limiting how much water it can fall from the tube into my t). In other words, he views the barometer as a balance, a tool for measuring (not just a tool for creating a vacuum), and since he is the first to see it in this way, he is traditionally regarded as the inventor of a barometer (in the sense we are now use the term).
Because rumors circulated in the Italian neighborhood of Italian gossip Torricelli, which included that he was involved in some form of magic or magic, Torricelli realized he had to keep the secret of his experiment to avoid the risk of being caught. He needs to use liquids that are heavier than water, and from previous associations and suggestions by Galileo, he concludes using mercury, shorter tubes can be used. With mercury, which is about 14 times denser than water, a tube of just 80 cm is now needed instead of 10.5 m.
In 1646, Blaise Pascal along with Pierre Petit, had repeated and perfected Torricelli's experiments after hearing about it from Marin Mersenne, who himself had been shown experiments by Torricelli towards the end of 1644. Pascal further designed his experiment to test Aristotle's proposition of steam from liquids which fills the space in the barometer. His experiments compare the water with wine, and because the latter is considered more "passionate", the Aristotelians expect the wine to stand lower (because more steam means more pressure on the liquid column). Pascal conducted the experiment openly, inviting the Aristotelians to predict the previous results. The Aristotle predicted the wine would stand lower. That does not.
However, Pascal goes even further to test the mechanical theory. If, as suspected by a mechanical philosopher such as Torricelli and Pascal, air has a lateral weight, the air weight will decrease at higher altitudes. Therefore, Pascal wrote to his brother-in-law, Florin Perier, who lived near a mountain called Puy de Dome, asking him to perform an important experiment. Perier will take a barometer up the Puy de Dome and make measurements along the height of the mercury column. He then compared it with measurements made at the foot of the mountain to see if the measurements taken higher turned out to be smaller. In September 1648, Perier carefully and carefully experimented, and found that Pascal's predictions were correct. The mercury barometer stands lower, the higher go.
Maps Barometer
Type
Water-based barometer
The concept that reduces atmospheric pressure predicts hurricane weather, postulated by Lucien Vidi, provides a theoretical base for weather predictors called "weather glass" or "Goethe barometer" (named after Johann Wolfgang Von Goethe, the famous German writer and polymath who developed a weatherball barometer that simple but effective use of the principle developed by Torricelli). The French name, le baromÃÆ'¨tre LiÃÆ'¨geois , is used by some English speakers. This name reflects the origins of many early weather glasses - glass blowers from LiÃÆ'¨ge, Belgium.
The weather ball barometer consists of a glass container with a sealed body, half filled with water. A narrow spout connects to the body beneath the surface of the water and rises above the surface of the water. The narrow drain is open to the atmosphere. When the air pressure is lower than when the body is sealed, the water level in the drain will rise above the water level inside the body; when the air pressure is higher, the water level in the drain will drop below the water level inside the body. Variations of this type of barometer can be easily made at home.
Mercury barometer
The mercury barometer has a vertical glass tube that is closed at the top, inside a basin containing open mercury at the bottom. The weight of mercury creates a vacuum at the top of the tube known as the Torricellian vacuum. The mercury in the tube adjusts to the weight of the mercury column to balance the atmospheric force applied to the reservoir. High atmospheric pressure places more force on the reservoir, forcing higher mercury in the column. Low pressure allows mercury to fall to lower levels in the column by lowering the force placed in the reservoir. Due to higher temperature levels around the instrument will reduce the density of mercury, the scale to read the height of mercury adjusted to compensate for this effect. The tube shall be at least as long as the amount of dip in the maximum mercury head space of the column.
Torricelli documented that the altitude of mercury in the barometer was little changed on a daily basis and concluded that this was due to the changing pressure in the atmosphere. He writes: "We live drowned in the bottom of a sea of ​​elementary air, known for experiments that can not be denied for weight." Inspired by Torricelli, Otto von Guericke on December 5, 1660 found that the air pressure was unbelievably low and predicted a storm, which occurred the next day.
The mercury barometer design raises the expression of atmospheric pressure in inches or millimeters or feet (torr): the pressure cited as the high level of mercury in the vertical column. Typically, atmospheric pressure is measured between 26.5 inches (670 mm) and 31.5 inches (800 mm) of Hg. One atmosphere (1 atm) is equivalent to 29.92 inches (760 mm) of mercury.
Design changes to make the instrument more sensitive, easier to read, and easier to move to produce variations such as basin, siphon, wheel, tank, Fortin, double folding, stereometric, and barometer balance. The Fitzroy barometer combines a standard mercury barometer with a thermometer, as well as a guide on how to interpret pressure changes. Fortin's barometer uses variable displacement mercury vials, usually built by pressing a puncture on the base of the skin diaphragm. This compensates for the displacement of mercury in the column with various pressures. To use the Fortin barometer, the mercury level is set to zero level before pressure is read on the column. Some models also use valves to seal the tank, allowing the mercury column to be forced into the top of the column to be transported. This prevents water hammer damage to the column during transit.
On June 5, 2007, the EU directive was enacted to limit mercury sales, effectively ending the production of a new mercury barometer in Europe.
Vacuum pump oil barometer
Using a vacuum pump oil as a working fluid in a barometer has led to the creation of a new "Highest Barometer in the World" in February 2013. The barometer at Portland State University (PSU) uses a double distilled distilled pump oil and has a nominal height of about 12.4 m for height oil column; expected visits are in the range of Ã, Â ± 0.4 m for a year. The Vacuum pumps have very low vapor pressure and are available in various densities; the lowest density vacuum oil is selected for the PSU barometer to maximize the height of the oil column.
Aneroid barometer
An aneroid barometer is an instrument used to measure pressure as a method that does not involve fluid. Created in 1844 by French scientist Lucien Vidi, aneroid barometers use a small flexible metal box called aneroid cells (capsules), made of beryllium and copper alloys. The evacuated capsules (or usually some capsules, stacked to supplement their movements) are prevented from collapsing by a strong spring. Small changes in external air pressure cause cells to expand or contract. This expansion and contraction push the mechanical lever so that the small motion of the capsule is strengthened and displayed on the face of aneroid barometer. Many models include manual set needles that are used to mark current measurements so that changes can be seen. In addition, the mechanism is purposely made "rigid" so tapping the barometer reveals whether the pressure rises or falls as the pointer moves. This type of barometer is common in homes and recreational boats, as well as small planes. It is also used in meteorology, mostly in barographs and as a pressure instrument in radiosondes.
Barograf
A barograph recorded the atmospheric pressure chart.
MEMS Barometer
The barometer of the microelectromechanical system (or MEMS) is a very small device between 1 and 100 micrometers in size (ie 0.001 to 0.1 mm). They are created through photolithography or photochemical machines. Typical applications include miniature weather stations, electronic barometers and altimeters.
The barometer can also be found on smartphones like Samsung Galaxy Nexus, Samsung Galaxy S3-S6, Motorola Xoom, Apple iPhone 6 smartphone, and Timex Expedition WS4 watches, based on MEMS technology and piezoresistive pressure-sensing. The inclusion of a barometer on a smartphone was originally intended to provide a faster GPS lock. However, third-party researchers can not confirm additional GPS accuracy or key speed due to barometric readings. The researchers suggest that the inclusion of a barometer on smartphones can provide a solution to determine user heights, but also suggests that some pitfalls must be addressed first.
A more unusual barometer
There are many more unusual barometer types. From variations on the storm barometer, such as the Patented Collins Barometer Table, to more traditional designs such as Hooke's Otheometer and Ross Sympiesometer. Some, such as the Shark Oil barometer, work only within a certain temperature range, achieved in warmer climates.
Apple
Air pressure and pressure tendencies (pressure changes over time) have been used in weather forecasting since the late 19th century. When used in combination with wind observations, accurate short-term estimates can be made. Simultaneous barometric readings of the entire weather station network allow the map of air pressure to be generated, which is the first form of a modern weather map when it was made in the 19th century. Isobar, the same line of pressure, when drawn on such a map, provides a contour map showing the high and low pressure areas. Localized local atmospheric pressure acts as a barrier to approaching the weather system, diverting their direction. The atmospheric lift caused by low-level wind convergence to the surface brings clouds and sometimes deposition. The greater the pressure changes, especially if more than 3.5 hPa (0.1 inHg), the greater the expected weather change. If the pressure drops rapidly, the low pressure system approaches, and there is a greater possibility of rain. The rapidly rising pressure, like the cold front behind, is associated with improved weather conditions, such as clear skies.
With the air pressure falling, the gas trapped inside the coal in the deep mine can escape more freely. Thus low pressure increases the risk of accumulation of letup. Collieries therefore keep track of the pressure. In the case of the Trimdon Grange Colmaneri disaster in 1882 the mining inspector drew attention to the record and in the report stated "atmospheric conditions and temperatures can be taken to reach dangerous spots".
Aneroid barometer is used in scuba diving. A submersible pressure gauge is used to track the contents of the air diver's tank. Other gauges are used to measure hydrostatic pressures, usually expressed as ocean depths. Good gauges or both can be replaced with electronic or dive variants.
Compensation
Temperature
The density of mercury will change with the increase or decrease in temperature, so the reading should be adjusted to the temperature of the instrument. For this purpose mercury thermometers are usually mounted on the instrument. Aneroid barometer temperature compensation is performed by incorporating bi-metal elements in mechanical connection. Aneroid barometers sold for domestic use usually do not have compensation based on the assumption that they will be used within the controlled room temperature range.
Altitude
When the air pressure decreases at an altitude above sea level (and rises below sea level) the uncorrected barometer reading will depend on its location. This reading is then adjusted to equivalent sea level pressure for reporting purposes. For example, if a barometer located at sea level and under fair weather conditions is moved to a height of 1,000 feet (305 m), about 1 inch of mercury (~ 35 hPa) should be added to the reading. Barometer readings at two locations should be the same if there are negligible changes in time, horizontal distance, and temperature. If this is not done, there will be a wrong indication of an approaching storm at higher altitude.
The aneroid barometer has a mechanical adjustment that allows equivalent seawater pressure to be read directly and without further adjustment if the instrument is not moved to different heights. Setting aneroid barometer is similar to reset an analog clock that is not in the right time. The dial is rotated so that the current atmospheric pressure from an accurate and nearest barometer (such as a local weather station) is displayed. No calculation is needed, since the source barometer reading has been converted to equivalent sea level pressure, and this is transferred to a regulated barometer - regardless of its height. Although somewhat rare, some aneroid barometers intended to monitor weather are calibrated to adjust altitude manually. In this case, knowing whether the current altitude or atmospheric pressure will be sufficient for accurate readings in the future.
The table below shows an example for three locations in the city of San Francisco, California. Note the corrected barometer reading is identical, and based on equivalent sea level pressure. (Assume temperature 15Ã, Â ° C.)
Barometer and atmospheric pressure calculation
When atmospheric pressure is measured by a barometer, the pressure is also referred to as "barometric pressure". Assume a barometer with cross-sectional area A , high h , filled with mercury from below at Point B upward at Point C. Pressure at the bottom of the barometer, Point B, is equal to the pressure atmosphere. The pressure at the top, Point C, can be considered zero because there is only mercury vapor above this point and the pressure is very low relative to atmospheric pressure. Therefore, one can find atmospheric pressure using a barometer and this equation:
P atm =? Gh
Where? is the mercury density, g is the acceleration of gravity, and h is the height of the mercury column above the free surface area. The physical dimension (tube length and tubular cross-sectional area) of the barometer itself does not affect the height of the liquid column inside the tube.
In thermodynamic calculations, the commonly used pressure unit is "standard atmosphere". This is the pressure generated from the 760 mm high mercury column at 0 ° C. For the density of mercury, use? Hg = 13,595 kg/m 3 and for the use of gravity acceleration g = 9,807 m/s 2 .
If water is used (not mercury) to meet standard atmospheric pressure, a water column of about 10.3 m (33.8 ft) will be required.
Standard atmospheric pressure as a function of height:
Note: 1 torr = 133.3 Pa = 0.03937 In Hg
- Upper Mount Everest, highest point on earth
Patent
- US 2194624, GA Titterington, Jr., "Diaphragm pressure gauge has a temperature compensation tool", issued 1940-03-26, set to Bendix Aviat Corp.
- AS. Patent 2,472,735 Ã,: C. J. UlrichÃ,: " Barometric Instruments "
- AS. Patent 2,691,305 Ã,: H. J. Frank: Barometric altimeter "
- AS. Patent 3,273,398 Ã,: D. C. W. T. Sharp: " Aneroid Barometer "
- AS. Patent 3,397,578 Ã,: H. A. Klumb: " Response mechanism of responsive motion pressure movement "
- AS. Patent 3,643,510 Ã,: F. Lissau: " fluid displacement pressure gauge "
- AS. Patent 4,106,342 Ã,: O. S. Sormunen: " Pressure gauge "
- AS. Patent 4,238,958 Ã,: H. DostmannÃ,: " Barometer "
- AS. Patents 4,327,583 Ã,: T. Fijimoto: " Weather forecast devices "
See also
References
Further reading
- Media related to Barometer on Wikimedia Commons
- Ã, "Barometer". EncyclopÃÆ'Â|dia Britannica . 3 (issue 11). 1911.
- Burch, David F. Barometer Handbook; a modern look on the barometer and barometer pressure applications. Seattle: Starpath Publications (2009), ISBN 978-0-914025-12-2.
- Middleton, W.E. Knowles. (1964). History of the barometer. Baltimore: Johns Hopkins Press. New edition (2002), ISBNÃ, 0-8018-7154-9.
Source of the article : Wikipedia
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