Editing Barometer (section)

== Types ==

=== Water barometers ===

[[File:Barometer Goethe 01.jpg|thumb|Goethe's device]]

The concept that decreasing atmospheric pressure predicts stormy weather, postulated by [[Lucien Vidi]], provides the theoretical basis for a weather prediction device called a "weather 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 barometer using the principles developed by [[Evangelista Torricelli|Torricelli]]).  The [[French language|French]] name, ''le baromètre Liègeois'', is used by some English speakers.<ref name="turner">Gerard L'E. Turner, ''Nineteenth Century Scientific Instruments'', Sotheby Publications, 1983, p. 236, {{ISBN|0-85667-170-3}}</ref>  This name reflects the origins of many early weather glasses – the glass blowers of [[Liège]], [[Belgium]].<ref name=turner /><ref name=zittle>Claus Zittle, ''Philosophies of Technology: Francis Bacon and His Contemporaries'', Brill 2008, pp. 115, 116 {{ISBN|90-04-17050-2}}</ref>

The weather ball barometer consists of a glass container with a sealed body, half filled with water.  A narrow spout connects to the body below the water level and rises above the 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 above 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 can be easily made at home.<ref name="JET">Jet Stream. [https://www.weather.gov/jetstream/ll_pressure Learning Lesson: Measure the Pressure – The "Wet" Barometer.] Retrieved on 2019-01-21.</ref> 

=== Mercury barometers ===
A [[Mercury (element)|mercury]] barometer is an instrument used to measure atmospheric pressure in a certain location and has a vertical glass tube closed at the top sitting in an open mercury-filled basin at the bottom. Mercury in the tube adjusts until the weight of it balances the atmospheric force exerted on the reservoir.  High atmospheric pressure 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 placed on the reservoir. Since higher temperature levels around the instrument will reduce the density of the mercury, the scale for reading the height of the mercury is adjusted to compensate for this effect.  The tube has to be at least as long as the amount dipping in the mercury + head space + the maximum length of the column.

[[File:MercuryBarometer.svg|thumb|left|Schematic drawing of a simple mercury barometer with vertical [[Mercury (element)|mercury]] column and reservoir at base]]

Torricelli 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 [[Earth's atmosphere|atmosphere]].<ref name="http://www.islandnet.com/~see/weather/history/barometerhistory1.htm"/>  He wrote: "We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight".<ref>Strangeways, Ian. ''Measuring the Natural Environment''. Cambridge University Press, 2000, p. 92.</ref> Inspired by Torricelli, [[Otto von Guericke]] on 5 December 1660 found that air pressure was unusually low and predicted a storm, which occurred the next day.<ref name="ley196606">{{Cite magazine
 |last=Ley
 |first=Willy
 |date=June 1966
 |title=The Re-Designed Solar System
 |department=For Your Information
 |url=https://archive.org/stream/Galaxy_v24n05_1966-06#page/n93/mode/2up
 |magazine=Galaxy Science Fiction
 |pages=94–106
}}</ref>

[[File:Baro 3.png|thumb|upright|Fortin barometer]]
The mercury barometer's design gives rise to the expression of atmospheric pressure in [[inch of mercury|inches]] or [[Millimeter of mercury|millimeters]] of mercury (mmHg).  A [[torr]] was originally defined as 1 mmHg.  The pressure is quoted as the level of the mercury's height in the vertical column.  Typically, atmospheric pressure is measured between {{convert|26.5|inch}} and {{convert|31.5|inch}} of Hg. One atmosphere (1 atm) is equivalent to {{convert|29.92|inch}} of mercury.

Design 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 folded, stereometric, and balance barometers.

In 2007, a [[European Union]] directive was enacted to restrict the use of mercury in new measuring instruments intended for the general public, effectively ending the production of new mercury barometers in Europe. The repair and trade of antiques (produced before late 1957) remained unrestricted.<ref name="eu reuters">{{cite news|url=https://www.reuters.com/article/environmentNews/idUSL0988544920070710|title=EU bans mercury in barometers, thermometers|author=Jones H.|date=10 July 2007|work=Reuters|access-date=12 September 2017}}</ref><ref>{{Cite web| url=https://www.europarl.europa.eu/sides/getDoc.do?type=IM-PRESS&reference=20070706IPR08897&language=EN| title=Ban on sale of mercury measuring instruments - MEPs agree two year exemption for barometers| date=10 July 2007| website=European Parliament| access-date=2021-05-11}}</ref>

==== Fitzroy barometer ====
[[Robert Fitzroy|''Fitzroy'']] barometers combine the standard mercury barometer with a thermometer, as well as a guide of how to interpret pressure changes.

==== Fortin barometer ====
[[File:Baro 2.png|thumb|upright|Reservoir of a Fortin barometer]]

[[Jean Nicolas Fortin|Fortin]] barometers use a variable displacement mercury cistern, usually constructed with a thumbscrew pressing on a leather diaphragm bottom (V in the diagram).  This compensates for displacement of mercury in the column with varying pressure.  To use a Fortin barometer, the level of mercury is set to zero by using the thumbscrew to make an ivory pointer (O in the diagram) just touch the surface of the mercury.  The pressure is then read on the column by adjusting the [[vernier scale]] so that the mercury just touches the sightline at Z.  Some 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 damage to the column in transit.

===Sympiesometer===
[[Image:Sympiesometer from A R Easton, Aberdeen.jpg|thumb|right|upright=0.5|Sympiesometer inscribed at bottom ''Improved sympiesometer'' and at top ''[[A R Easton]], 53 Marischal Street, Aberdeen.'' Owned by descendants of the [[Aberdeen]] shipbuilding [[Hall]] family.]]

A [[sympiesometer]] is a compact and lightweight barometer that was widely used on ships in the early 19th century.  The sensitivity of this barometer was also used to measure altitude.<ref name=Stanton>{{cite book|last1=Stanton|first1=William|title=The Great United States Exploring Expedition|date=1975|publisher=University of California Press|location=Berkeley|isbn=0520025571|page=[https://archive.org/details/greatunitedstate00will/page/126 126]|url-access=registration|url=https://archive.org/details/greatunitedstate00will/page/126}}</ref>

Sympiesometers have two parts. One is a traditional [[mercury thermometer]] that is needed to calculate the expansion or contraction of the fluid in the barometer. The other is the barometer, consisting of a J-shaped tube open at the lower end and closed at the top, with small reservoirs at both ends of the tube.

In 1778, Blondeau developed an iron tube barometer using narrow-bore musket barrels. This design resulted in a durable and polished instrument that resisted mercury corrosion and minimized breakage from the ship's movement.<ref name=":3" />

=== Marine Barometer ===
The need for a practical marine barometer arose from the urgent necessity of weather prediction at sea, where sailors faced frequent, and often dangerous, changes in wind, calm, and storm conditions.<ref name=":3" /> Traditional mercury barometers, though useful on land, proved unreliable on ships due to their susceptibility to the ship’s motion.<ref name=":3" /> Oscillations caused the mercury to strike the top of the glass tube, leading to frequent breakage and making air pressure readings nearly impossible to interpret accurately during voyages.<ref name=":3" />

[[Roger North (biographer)|Roger North]] observed that many, including [[Robert Hooke]], attempted to resolve these issues but often abandoned the endeavor due to technical limitations.<ref name=":3" /> Nonetheless, Hooke remained persistent, proposing several adaptations including narrowing the open end of the siphon tube and exploring spiral tube designs.<ref name=":3" /> His most notable contribution was the creation of a double thermometer marine barometer, also referred to as a manometer, which was presented to the [[Royal Society]] in 1668 and constructed by Henry Hunt.<ref name=":3" />

Hooke’s marine barometer marked a turning point in the development of nautical meteorological tools. It featured a compact, affordable design tailored for maritime use, becoming the first instrument specifically constructed for sailors.<ref name=":3" /> The device combined a sealed spirit thermometer with an open air-based thermometer, calibrated to reflect barometric pressure changes through liquid displacement<ref name=":12">{{Cite journal |last=Halley |first=Edmund |date=1683–1775 |title=An Account of Dr Robert Hook's Invention of the Marine Barometer |journal=Philosophical Transactions |volume=22 |pages=791–794 |doi=10.1098/rstl.1700.0074 |jstor=}}</ref><ref name=":4">{{Cite web |date=2025-02-02 |title=Torricelli and the Ocean of Air: The First Measurement of Barometric Pressure - PMC |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3768090/ |access-date=2025-03-21 |website=web.archive.org |archive-date=2025-02-02 |archive-url=https://web.archive.org/web/20250202182642/https://pmc.ncbi.nlm.nih.gov/articles/PMC3768090/ |url-status=bot: unknown }}</ref>. Hooke’s use of hydrogen-filled containers and colorful almond oil further enhanced visibility and responsiveness.<ref name=":32">{{Cite journal |last1=Ward |first1=Catharine |last2=Dowdeswell |first2=Julian |date=August 2006 |title=On the Meteorological Instruments and Observations Made during the 19th Century Exploration of the Canadian Northwest Passage |journal=Arctic, Antarctic, and Alpine Research |volume=38 |issue=3 |pages=454–464 |doi=10.1657/1523-0430(2006)38[454:OTMIAO]2.0.CO;2 |jstor=}}</ref> Notably, [[Edmond Halley|Edmund Halley]] tested this prototype on his South Atlantic voyage from 1698 to 1700 and praised its reliability in forecasting weather changes.<ref name=":3" /><ref name=":12" /> His endorsement led to greater interest and validation by the Royal Society.<ref name=":3" /><ref name=":12" /> Figure 8 below is from this report, depicting the Hooke Barometer, with detailed description in the writing.<ref name=":12" />

[[File:Stick Barometer.png|thumb|Figure 8 from Robert Hooke's Barometer Invention|left|455x455px]]

Building on Hooke’s foundation, John Patrick sought to improve the design by replacing the water with mercury, advertising his version as a “new marine barometer.”<ref name=":3" /> Though some criticized it for the difficulty of reading the mercury column due to shipboard vibrations, navigator [[Christopher Middleton (navigator)|Christopher Middleton]] employed it during expeditions to Hudson's Bay.<ref name=":3" /> He consistently found it effective in forecasting storms, wind changes, and even the proximity of ice.<ref name=":3" />

A significant advancement occurred during [[James Cook|Captain James Cook]]’s renowned voyages in the late 18th century.<ref name=":3" /> As part of preparations for Cook’s second Pacific expedition (1772–1775), the Board of Longitude and the Royal Society commissioned the production of marine barometers.<ref name=":3" /> Renowned instrument maker [[Edward Nairne]] was chosen to supply the equipment.<ref name=":3" /> Contrary to expectations for spiral tubes, Nairne opted for straight, constricted tubes mounted on boards, coupled with a gimbaled suspension system to ensure vertical orientation and stability at sea.<ref name=":3" />

Nairne’s design represented a leap in functionality. The narrow bore significantly reduced mercury motion, enabling more accurate readings even in turbulent conditions.<ref name=":3" /> These instruments proved so reliable that they were adopted not only by the [[Royal Navy]] but also by international expeditions.<ref name=":3" /> The [[East India Company]], Russian explorers, and French and Spanish navigators, including [[Jean-François de Galaup, comte de Lapérouse]] (voyage in 1785) and [[Alejandro Malaspina|Alessandro Malaspina]] (voyage in 1789), incorporated variants of Nairne’s barometer into their voyages.<ref name=":3" />

Despite the widespread use of Nairne’s marine barometer, it was not without limitations.<ref name=":13">{{Cite journal |title=1944JRASC..38...41K Page 41 |url=https://adsabs.harvard.edu/full/1944JRASC..38...41K |access-date=2025-03-21 |journal=Journal of the Royal Astronomical Society of Canada|bibcode=1944JRASC..38...41K |last1=Knowles Middleton |first1=W. E. |date=1944 |volume=38 |page=41 }}</ref> Lapérouse lauded the device’s predictive capabilities but also noted inconsistencies in mercury behavior, highlighting the complexity of translating instrument readings into reliable forecasts.<ref name=":13" /> In response to the fragility of glass tubes, other scientists, such as Le Roy, proposed alternate models like the folded Huygens barometer, designed for enhanced durability and reduced oscillation aboard ships.<ref name=":13" />

The marine barometer’s practical value was reaffirmed in 1801 when the [[Royal Society]] sent Captain [[Matthew Flinders]] on a three-year voyage from New Holland to New South Wales, equipped with one of Nairne’s barometers.<ref name=":22">{{Cite journal |last=Flinders |first=Matthew |date=1806 |title=Observations upon the Marine Barometer |journal=Philosophical Transactions of the Royal Society of London |volume=96 |pages=239–266 |jstor=}}</ref> In his official correspondence, Flinders confirmed the instrument’s success and expressed appreciation for its stability and precision in recording atmospheric conditions.<ref name=":22" />

Throughout its evolution, the marine barometer transitioned from a theoretical invention to a critical navigational and meteorological tool. Its development not only reflected ingenuity in overcoming the challenges of shipboard instrumentation but also underscored its importance in the broader context of global exploration. These devices empowered mariners to make informed decisions, contributing to safer and more efficient voyages across the world's oceans.  

==== Wheel barometers ====
A wheel barometer uses a "J" tube sealed at the top of the longer limb.  The shorter limb is open to the atmosphere, and floating on top of the mercury there is a small glass float.  A fine silken thread is attached to the float which passes up over a wheel and then back down to a counterweight (usually protected in another tube).  The wheel turns the point on the front of the barometer.  As atmospheric pressure increases, mercury moves from the short to the long limb, the float falls, and the pointer moves.  When pressure falls, the mercury moves back, lifting the float and turning the dial the other way.<ref>{{cite web|last=Hood|first=Jean|title=Barometers : History, working and styles|date=5 December 2017|url=http://www.jeanhood.co.uk/barometers_history_and_styles_etc.html|access-date=21 June 2020}}</ref>

Around 1810 the wheel barometer, which could be read from a great distance, became the first practical and commercial instrument favoured by farmers and the educated classes in the UK. The face of the barometer was circular with a simple dial pointing to an easily readable scale: "Rain - Change - Dry" with the "Change" at the top centre of the dial. Later models added a barometric scale with finer graduations: "Stormy (28 inches of mercury), Much Rain (28.5), Rain (29), Change (29.5), Fair (30), Set fair (30.5), very dry (31)".

Natalo Aiano is recognised as one of the finest makers of wheel barometers, an early pioneer in a wave of artisanal Italian instrument and barometer makers that were encouraged to emigrate to the UK. He listed as working in Holborn, London {{circa|1785}}–1805.<ref>{{cite web |title=Natalo Aiano |url=https://www.aianos.co.uk/about-us/ |website=About us page |date=22 May 2017 |publisher=C. Aiano & Sons Ltd.}}</ref> From 1770 onwards, a large number of Italians came to England because they were accomplished glass blowers or instrument makers. By 1840 it was fair to say that the Italians dominated the industry in England.<ref>{{cite book |last1=Nicholas |first1=Goodison |title=English barometers 1680–1860 : a history of domestic barometers and their makers and retailers |date=1977 |publisher=Antique Collectors' Club |isbn=978-0902028524 |edition=Rev. and enl.}}</ref>

===Vacuum pump oil barometer===

Using 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 University (PSU) uses doubly distilled vacuum pump oil and has a nominal height of about 12.4&nbsp;m for the oil column height; expected excursions are in the range of ±0.4&nbsp;m over the course of a year. Vacuum pump oil has very low vapour pressure and is available in a range of densities; the lowest density vacuum oil was chosen for the PSU barometer to maximize the oil column height.<ref>Tomlinson, Stuart (February 10, 2013) [http://www.oregonlive.com/portland/index.ssf/2013/02/large_barometer_at_portland_st.html Large barometer at Portland State University could be the tallest in the world]. oregonlive.com</ref>

=== Aneroid barometers ===
[[File:Modern Aneroid Barometer.jpg|thumb|Aneroid barometer]]

An aneroid barometer is an [[Measuring instrument|instrument]] used for measuring air pressure via a method that does not involve [[liquid]]. Although Gottfried Wilhelm Leibniz first proposed the concept of an aneroid barometer around 1700, it was not until 1844 that French scientist Lucien Vidi successfully invented it.<ref name="http://www.islandnet.com/~see/weather/history/barometerhistory1.htm" /> The aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an [[alloy]] of [[beryllium]] and [[copper]].<ref name="r1">{{cite book |author1=Figuier, Louis |url=https://archive.org/details/bub_gb_Cus0AAAAMAAJ |title=L'Année scientifique et industrielle |author2=Gautier, Émile |publisher=L. Hachette et cie. |year=1867 |pages=[https://archive.org/details/bub_gb_Cus0AAAAMAAJ/page/n495 485]–486}}</ref> The evacuated capsule (or usually several capsules, stacked to add up their movements) 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 that a relative change can be seen. This type of barometer is common in homes and in [[recreational boat]]s. It is also used in [[meteorology]], mostly in [[barograph]]s, and as a pressure instrument in [[radiosonde]]s.

==== Barographs ====

{{Main article|Barograph}}

[[File:Barograph 01.jpg|thumb|Analogue recording [[barograph]] using five stacked aneroid barometer cells]]A barograph is a recording aneroid barometer where the changes in atmospheric pressure are recorded on a paper chart.

The principle of the barograph is same as that of the aneroid barometer. Whereas the barometer displays the pressure on a dial, the barograph uses the small movements of the box to transmit by a system of levers to a recording arm that has at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper using ink, held in a nib. The recording material is mounted on a cylindrical drum which is rotated slowly by a clock. Commonly, the drum makes one revolution per day, per week, or per month, and the rotation rate can often be selected by the user.

=== <span id="MEMS Barometers"></span>MEMS barometers ===
[[File:Galaxy Nexus smartphone.jpg|thumb|110px|The [[Galaxy Nexus]] has a built-in barometer]]
[[Microelectromechanical systems]] (or MEMS) barometers are extremely small devices between 1 and 100 micrometres in size (0.001 to 0.1&nbsp;mm). They are created via [[photolithography]] or [[photochemical machining]]. Typical applications include miniaturized weather stations, electronic barometers and altimeters.<ref>{{cite journal |journal =Sensors & Transducers E-Digest |volume=92 |issue=4 |year=2008 |title=MEMS Barometric Pressure Sensor|url=http://www.sensorsportal.com/HTML/DIGEST/may_08/MEMS_pressure_sensor.htm |access-date=13 June 2014}}</ref>

A barometer can also be found in smartphones such as the Samsung [[Galaxy Nexus]],<ref>[https://gizmodo.com/5851133/this-is-the-samsung-galaxy-nexus-googles-new-official-android-phone This Is the Samsung Galaxy Nexus, Google's New Official Android Phone] {{Webarchive|url=https://web.archive.org/web/20120810045436/http://gizmodo.com/5851133/this-is-the-samsung-galaxy-nexus-googles-new-official-android-phone |date=2012-08-10 }}. Gizmodo.com (2011-10-18). Retrieved on 2011-11-15.</ref> Samsung Galaxy S3-S6, Motorola Xoom, Apple [[iPhone 6]] and newer iPhones, and [[Timex Expedition WS4]] [[smartwatch]], based on [[Microelectromechanical systems|MEMS]] and [[Pressure sensor#Pressure-sensing technology|piezoresistive pressure-sensing]] technologies.<ref>{{cite news |last=Molen |first=Brad |url=https://www.engadget.com/2011/10/20/behind-the-glass-a-detailed-tour-inside-the-samsung-galaxy-nexu/ |title=Behind the glass: a detailed tour inside the Samsung Galaxy Nexus |work=[[Engadget]] |publisher=[[Engadget]] |date=2011-10-20 |url-status=live |archive-url=https://web.archive.org/web/20141205163527/http://www.engadget.com/2011/10/20/behind-the-glass-a-detailed-tour-inside-the-samsung-galaxy-nexu/ |archive-date=2014-12-05 |access-date=2015-06-23 |quote=Barometric pressure sensor: Bosch BMP180 }}</ref><ref>{{cite web|url=http://ae-bst.resource.bosch.com/media/downloads/pressure/bmp180/Flyer_BMP180_08_2013_web.pdf |title=BMP180: Digital, barometric pressure sensor |work=[[Robert Bosch GmbH|Bosch]] |access-date=2015-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20150623102607/http://ae-bst.resource.bosch.com/media/downloads/pressure/bmp180/Flyer_BMP180_08_2013_web.pdf |archive-date=2015-06-23 }}</ref> Inclusion of barometers on smartphones was originally intended to provide a faster [[Global Positioning System|GPS]] lock.<ref>[https://www.engadget.com/2011/10/20/galaxy-nexus-barometer-explained-sam-champion-not-out-of-a-job/ Galaxy Nexus barometer explained, Sam Champion not out of a job]. Engadget (2011-10-20). Retrieved on 2011-12-03.</ref> However, [[Microsoft Research|third party researchers]] were unable to confirm additional GPS accuracy or lock speed due to barometric readings. The researchers suggest that the inclusion of barometers in smartphones may provide a solution for determining a user's elevation, but also suggest that several pitfalls must first be overcome.<ref>{{cite journal |title=Barometric Phone Sensors – More Hype Than Hope! |journal=ACM HotMobile |date=2014-02-26 |last1=Muralidharan |first1=Kartik |last2=Khan |first2=Azeem Javed |last3=Misra |first3=Archan |last4=Balan |first4=Rajesh Krishna |last5=Agarwal |first5=Sharad |page=2 |url=http://research.microsoft.com/apps/pubs/default.aspx?id=206442 |access-date=2015-06-23 }}</ref>

=== More unusual barometers ===
[[File:Timex Expedition WS4 Barometric chart peaks cloudy close up.jpg|thumb|110px|Timex Expedition WS4 in Barometric chart mode with weather forecast function]]

There are many other more unusual types of barometer. From variations on the storm barometer, such as the Collins Patent Table Barometer, to more traditional-looking designs such as Hooke's Otheometer and the Ross Sympiesometer. Some, such as the Shark Oil barometer,<ref>[http://www.barometerworld.co.uk/articles.htm#sharkoil Shark Oil Barometer] {{webarchive |url=https://web.archive.org/web/20110720091837/http://www.barometerworld.co.uk/articles.htm#sharkoil |date=July 20, 2011 }} Barometer World.</ref> work only in a certain temperature range, achieved in warmer climates.