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d aneroid barometerModern aneroid barometer

1646, Blaise Pascal along with Pierre Petit, had repeated and perfected Torricelli's experiment after hearing about it from Marin Mersenne, who himself had been shown the

eriment by Torricelli toward the end of 1644. Pascal further devised an experiment to test the Aristotelian proposition that it was vapors from the liquid that filled the space

a barometer. His experiment compared water with wine, and since the latter was considered more "spiritous", the Aristotelians expected the wine to stand lower (since more

ors would mean more pushing down on the liquid column). Pascal performed the experiment publicly, inviting the Aristotelians to predict the outcome beforehand. The

stotelians predicted the wine would stand lower. It did not.[6]

wever, Pascal went even further to test the mechanical theory. If, as suspected by mechanical philosophers like Torricelli and Pascal, air had lateral weight, the weight of the

would be less at higher altitudes. Therefore, Pascal wrote to his brother-in-law, Florin Perier, who lived near a mountain called the Puy de Dome, asking him to perform a

cial experiment. Perier was to take a barometer up the Puy de Dome and make measurements along the way of the height of the column of mercury. He was then to compare

o measurements taken at the foot of the mountain to see if those measurements taken higher up were in fact smaller. In September 1648, Perier carefully and meticulously

ried out the experiment, and found that Pascal's predictions had been correct. The mercury barometer stood lower the higher one went.[6]

ypes

ater-based barometers

e concept that decreasing atmospheric pressure predicts stormy weather, postulated by Lucien Vidie, provides the theoretical basis for a weather prediction device called a

orm glass" or a "Goethe barometer" (named for Johann Wolfgang Von Goethe, the renowned German writer and polymath who developed a simple but effective weather ball

ometer using the principles developed by Torricelli).

e weather ball barometer consists of a glass container with a sealed body, half f illed with water. A narrow spout connects to the body below the water level and rises above

water level. The narrow spout is open to the atmosphere. When the air pressure is lower than it was at the time the body was sealed, the water level in the spout will rise

ve the water level in the body; when the air pressure is higher, the water level in the spout will drop below the water level in the body. A variation of this type of barometer

be easily made at home.[9]

ercury barometers

mercury barometer has a glass tube with a height of at least 84 cm, closed at one end, with an open mercury-filled reservoir at the base. The weight of the mercury creates a

uum in the top of the tube. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. High atmosphericssure places more force on the reservoir, forcing mercury higher in the column. Low pressure allows the mercury to drop to a lower level in the column by lowering the force

ced on the reservoir. Since higher temperature at the instrument will reduce the density of the mercury, the scale for reading the height of the mercury is adjusted to

mpensate for this effect.

rricelli documented that the height of the mercury in a barometer changed slightly each day and concluded that this was due to the changing pressure in the atmosphere.[1]

wrote: "We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight"[source?].

e mercury barometer's design gives rise to the expression of atmospheric pressure in inches or millimeters or feet (torr): the pressure is quoted as the level of the mercury's

ght in the vertical column. Typically, atmospheric pressure is measured between 26.5 to 31.5 inHg. One atmosphere (1 atm) is equivalent to 760 millimeters of mercury.

sign changes to make the instrument more sensitive, simpler to read, and easier to transport resulted in variations such as the basin, siphon, wheel, cistern, Fortin, multiple

ded, stereometric, and balance barometers. Fitzroy barometers combine the standard mercury barometer with a thermometer, as well as a guide of how to interpret pressure

nges. Fortin barometers use a variable displacement mercury cistern, usually constructed with a thumbscrew pressing on a leather diaphragm bottom. This compensates for

placement of mercury in the column with varying pressure. To use a Fortin barometer, the level of mercury is set to the zero level before the pressure is read on the column.

me models also employ a valve for closing the cistern, enabling the mercury column to be forced to the top of the column for transport. This prevents water-hammer damagehe column in transit.

June 5, 2007, a European Union directive was enacted to restrict the sale of mercury, thus effectively ending the production of new mercury barometers in Europe.

acuum pump oil barometer

ng vacuum pump oil as the working fluid in a barometer has led to the creation of the new "World's Tallest Barometer" in February 2013. The barometer at Portland State

iversity (PSU) uses doubly distilled vacuum pump oil and has a nominal height of ~12.4 m for the oil column height; expected excursions are in the range of 0.4 m over the

rse of a year. Vacuum pump oil has very low vapor pressure and it is available in a range of densities; the lowest density vacuum oil was chosen for the PSU barometer to

ximize the oil column height.[10]

neroid barometers

See also: Barograph

An aneroid barometer, invented in 1843 by French scientist Lucien Vidie uses a small,

flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium

and copper.[11] The evacuated capsule (or usually more capsules) is prevented from collapsing

by a strong spring. Small changes in external air pressure cause the cell to expand or contract.

This expansion and contraction drives mechanical levers such that the tiny movements of the

capsule are amplified and displayed on the face of the aneroid barometer. Many models include

a manually set needle which is used to mark the current measurement so a change can be seen.

In addition, the mechanism is made deliberately "stiff" so that tapping the barometer reveals

whether the pressure is rising or falling as the pointer moves.

Barographs

arograph, which records a graph of some atmospheric pressure, uses an aneroid barometer mechanism to move a needle on a smoked foil or to move a pen upon paper, both

which are attached to a drum moved by clockwork.[12]

ore unusual barometers

ere are many other more unusual types of barometer. From variations on the storm barometer, such as the Collins Patent Table Barometer, to more

ditional looking designs such as Hooke's Otheometer and the Ross Sympiesometer. Some, such as the Shark Oil barometer,[14] work only in a certain

mperature range, achieved in warmer climates

arometer can also be found in smartphones such as the Samsung Galaxy Nexus smartphone,[15] which is included to provide a faster GPS lock.[16]

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The Galaxy Nexus

has a built-in

barometer[13]

gital graphing barometer.

Barograph using five stacked aneroid

barometercells.

Table ofPneumaticks, 1728 Cyclopaedia

pplications

See also: Surface weather analysis and Weather forecasting

Using barometric pressure and the pressure tendency (the change of pressure over time) has been used in weather

forecasting since the late 19th century.[17] When used in combination with wind observations, reasonably

accurate short-term forecasts can be made.[18] Simultaneous barometric readings from across a network of

weather stations allow maps of air pressure to be produced, which were the first form of the modern weather

map when created in the 19th century. Isobars, lines of equal pressure, when drawn on such a map, gives a

contour map showing areas of high and low pressure.[19] Localized high atmospheric pressure acts as a barrier to

approaching weather systems, diverting their course. Atmospheric lift caused by low-level wind convergence into

the surface low brings clouds and potentially precipitation.[20] The larger the change in pressure, especially if

more than 3.5 hPa, the larger the change in weather can be expected. If the pressure drop is

rapid, a low pressure system is approaching, and there is a greater chance of rain . Rapidpressure rises, such as in the wake of a cold front, are associated with improving weather

nditions, such as clearing skies.[21]

ompensations

mperature

e density of mercury will change with temperature, so a reading must be adjusted for the temperature of the instrument. For this

pose a mercury thermometer is usually mounted on the instrument. Temperature compensation of an aneroid barometer is

omplished by including a bi-metal element in the mechanical linkages. Aneroid barometers sold for domestic use typically have no

mpensation.

titude

the air pressure will be decreased at altitudes above sea level (and increased below sea level) the actual reading of the instrument will be dependent upon its location. This

ssure is then converted to an equivalent sea-level pressure for purposes of reporting and for adjusting aircraft altimeters (as aircraft may fly between regions of varying

malized atmospheric pressure owing to the presence of weather systems). Aneroid barometers have a mechanical adjustment for altitude that allows the equivalent sea level

ssure to be read directly and without further adjustment if the instrument is not moved to a different altitude.

atents

US 2194624 (http://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US2194624), G. A. Titterington, Jr,

"Diaphragm pressure gauge having temperature compensating means", issued 1940-03-26, assigned to Bendix Aviat Corp

U.S. Patent 2,472,735 (http://www.google.com/patents?vid=2472735) : C. J. Ulrich : "Barometric instrument"

U.S. Patent 2,691,305 (http://www.google.com/patents?vid=2691305) : H. J. Frank : Barometric altimeter"

U.S. Patent 3,273,398 (http://www.google.com/patents?vid=3273398) : D. C. W. T. Sharp : "Aneroid barometer"

U.S. Patent 3,397,578 (http://www.google.com/patents?vid=3397578) : H. A. Klumb : "Motion amplifying mechanism for

pressure responsive instrument movement"

U.S. Patent 3,643,510 (http://www.google.com/patents?vid=3643510) : F. Lissau : "Fluid displacement pressure gauges"U.S. Patent 4,106,342 (http://www.google.com/patents?vid=4106342) : O. S. Sormunen : "Pressure measuring instrument"

U.S. Patent 4,238,958 (http://www.google.com/patents?vid=4238958) : H. Dostmann : "Barometer"

U.S. Patent 4,327,583 (http://www.google.com/patents?vid=4327583) : T. Fijimoto : "Weather forecasting device"

ee also

Automated airport weather station

Barograph

Barometer question

Bert Bolle Barometer

Ilmakiur A barometer made of stone

Microbarometer

Robert FitzRoy#Meteorology

Storm glassSurface weather analysis

Tempest Prognosticator

Weather forecasting

eferences

1. ^a b c d

"The Invention of the Barometer" (http://www.islandnet.com/~see/weather/history/barometerhistory1.htm). Islandnet.com. Retrieved 2010-02-04.

2. ^ "Historyof the Barometer"(http://www.barometerfair.com/history_of_the_barometer.htm). Barometerfair.com. Retrieved 2010-02-04.

3. ^ "Evangelista Torricelli,The Invention of the Barometer"(http://www.juliantrubin.com/bigten/torricellibarometer.html). Juliantrubin.com. Archived (http://web.archive.org/

web/20100209094157/http://www.juliantrubin.com/bigten/torricellibarometer.html) from

the original on 9 February2010. Retrieved 2010-02-04.

4. ^ Drake, Stillman(1970). "Berti,Gasparo".Dictionary of Scientific Biography 2. NewYork:Charles Scribner's Sons. pp. 8384. ISBN 0-684-10114-9.

5. ^ WilliamR. Shea (2003).Designing Experiments & Games of Chance: The

Unconventional Science of Blaise Pascal (http://books.google.com/books?id=-

x6B1Q5UoE4C&pg=PA21). Science HistoryPublications. pp. 21.

ISBN 978-0-88135-376-1. Retrieved 10 October 2012.

6. ^a b c d e f

"Historyof the Barometer" (http://www.strange-loops.com/scibarometer.html).Strange-loops.com.2002-01-21. Archived (http://web.archive.org/web/20100106074525/

http://www.strange-loops.com/scibarometer.html) from the original on 6 January 2010.

Retrieved 2010-02-04.

7. ^ "Torricelli's letter to Michelangelo Ricci"(http://web.lemoyne.edu/~giunta/torr.html).Web.lemoyne.edu.Retrieved 2010-02-04.

8. ^ "Brief Historyof the Barometer" (http://www.barometer.ws/history.html). Barometer.ws.Archived (http://web.archive.org/web/20100114144734/http://www.barometer.ws/

history.html) from the original on 14 January 2010. Retrieved 2010-02-04.

9. ^ Jet Stream. Learning Lesson:Measure the Pressure The "Wet" Barometer. (http://

www.srh.weather.gov/jetstream/atmos/ll_pressure.htm) Retrieved on 2007-05-05.

10. ^ Tomlinson, Stuart (February10, 2013) Large barometer at Portland State Universitycould

be the tallest in the world (http://www.oregonlive.com/portland/index.ssf/2013/02/large_

barometer_at_portland_st.html). oregonlive.com11. ^ Enotes.com. How Products Are Made: AneroidBarometer. (http://science.enotes.com/

how-products-encyclopedia/aneroid-barometer) Retrieved on 2007-05-05.

12. ^ Glossaryof Meteorology.Barograph. (http://amsglossary.allenpress.com/glossary/search?id=barograph1) Retrieved on 2007-05-05.

13. ^ GalaxyNexus (http://www.google.com/nexus/#/tech-specs). Google.com.Retrieved on2011-12-03.

14. ^ Shark Oil Barometer Barometer World (http://www.barometerworld.co.uk/articles.htm#sharkoil) Retrieved on 2009-09-26.

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5. ^ This Is the Samsung GalaxyNexus,Google's New Official AndroidPhone (http://

gizmodo.com/5851133/this-is-the-samsung-galaxy-nexus-googles-new-official-android-phone). Gizmodo.com (2011-10-18). Retrieved on 2011-11-15.

6. ^ GalaxyNexus barometer explained,Sam Champion not out of a job (http://www.engadget.com/2011/10/20/galaxy-nexus-barometer-explained-sam-champion-not-out-

of-a-job/).Engadget (2011-10-20).Retrieved on 2011-12-03.

7. ^ USA Today. Understanding air pressure. (http://www.usatoday.com/weather/

wbarocx.htm) Retrieved on 2008-05-25.

8. ^ USA Today. Using winds and abarometerto make forecasts. (http://www.usatoday.com/

weather/wfbarrow.htm) Retrieved on 2007-05-05.

19. ^ Edward J.Hopkins,Ph.D. (1996-06-10). "Surface Weather AnalysisChart" (http://

www.meteor.wisc.edu/~hopkins/aos100/sfc-anl.htm).Universityof Wisconsin.Archived(http://web.archive.org/web/20070428121643/http://www.meteor.wisc.edu/~hopkins/

aos100/sfc-anl.htm) from the original on 28 April 2007. Retrieved 2007-05-10.

20. ^ Robert Penrose Pearce (2002).Meteorology at the Millennium (http://books.google.com/?

id=QECy_UBdyrcC&pg=PA66). AcademicPress. p. 66. ISBN 978-0-12-548035-2.

Retrieved 2009-01-02.

21. ^ Weather Doctor.Applying The Barometer To Weather Watching. (http://www.islandnet.com/~see/weather/eyes/barometer3.htm) Retrieved on 2008-05-25.

urther reading

Burch, David F. The Barometer Handbook; a modern look at barometers and applications of barometric pressure. Seattle: Starpath Publications (2009), ISBN

978-0-914025-12-2.

Middleton, W.E. Knowles. (1964). The history of the barometer. Baltimore: Johns Hopkins Press. New edition (2002), ISBN 0-8018-7154-9.

rieved from "http://en.wikipedia.org/w/index.php?title=Barometer&oldid=548102041"

egories: Pressure gauges Meteorological instrumentation and equipment Glass applications Italian inventions

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