Aneroid Barometer,Aneroid Barometer inventors | edubilla.com : Physics About Invention An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid. Invented in 1844 by French scientist Lucien Vidi,the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. 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. This type of barometer is common in homes and in recreational boats but also used in meteorology, mostly as barograph and pressure instruments in radiosondes.

Vintage Aneroid Wooden Barometer For Sale in Swords, Dublin from JusPav Vintage Aneroid wooden barometer Description (last update: 1 year ago) Made in Germany. An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid. Invented in 1844 by French scientist Lucien Vidi. This type of barometer is common in homes and inrecreational boats, as well as small aircraft. It is also used in meteorology, mostly inbarographs and as a pressure instrument inradiosondes. Shipping: Collection Barometers Barometers Rare Antique German DRGM Enamel barometer, probably Copenhagen image Posted on September 28, 2016 and filed under Uncategorized . Enamel is in excellent condition. Marked DRGM on the back. The item “Rare Antique German DRGM Enamel barometer, probably Copenhagen image” is in sale since Wednesday, September 28, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “idlaantique” and is located in Tallinn, Harjumaa.

This item can be shipped worldwide. Antique Central Scientific Brass / Copper Barometer mounted on Mahogany Posted on September 28, 2016 and filed under Uncategorized . This barometer was manufactured by the Central Scientific Co. By the color of the metal most of the material composition, besides the wood base, appears to be brass. I believe the wood is mahogany, but it is difficult to tell. Please use photos to determine the wood type. The second plaque indicates that it was originally Government and University of Chicago property. The round glass piece at the bottom of the barometer is complete. Based on feedback from buyers, the original barometer had a round glass tube inside the brass tube. THERE IS NO GLASS TUBE INSIDE. The glass thermometer is completely intact and works. In regards to the condition, there is discoloration and staining that is normal for an item of this age. The wood appears to have been newly stained and redone. There is gouging on the wood at the top (see photo). The brass part from end to end measures about 39.5 long. The wood base measures 42.75″ long and about 4-3/8″ wide.

All together it weighs about 5 lbs 6 oz. It will be appropriately packed. Please use photos to best determine value and condition. The item “Antique Central Scientific Brass / Copper Barometer mounted on Mahogany” is in sale since Tuesday, September 27, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “mayevsky” and is located in Goshen, Indiana. This item can be shipped to United States. Maker: Central Scientific Co. Beautiful Vtg Antique 19th C. Inlaid Banjo Barometer Thermometer Dolland London Posted on September 27, 2016 and filed under Uncategorized . Get Vendio Gallery – Now FREE! Vintage antique 19th century barometer thermometer. Barometer made by Dolland in London No. Barometer measures 6 in diameter. Has not been tested, but appears to work. Follow us on Facebook. Sign up for our newsletter. I expect to be paid within 5 days. We strive to charge rates that are fair, and as low as possible.

The item “Beautiful Vtg Antique 19th C. Inlaid Banjo Barometer Thermometer Dolland London” is in sale since Tuesday, September 20, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “privatescreening” and is located in Seattle, Washington. This item can be shipped worldwide. Original/Reproduction: Original Antique Black Forest Wood Carving Thermometer Barometer Hunt Fox Crow Paris Posted on September 27, 2016 and filed under Uncategorized . Antique French Black Forest Wood Carving Thermometer Barometer Hunt Fox Crow Paris. The wood is beautifully carved, probably linden wood, and stained a rich walnut brown. The decor of grape leaves, two birds, and the head of a fox, all carved in a cut out pattern. The decor refers to Aesop’s fable of the fox and the crow. The thermometer is in Centigrade and Reaumur. The barometer is in brass and the dial looks to be enameled metal. The thermometer is glass and porcelain enameled metal.

The barometer is marked Patoueille from Paris (see photos). It measures 27 1/2″ tall, 12 1/4″ wide, and 2 1/2 deep. Some discoloration under the glass on the rim of the barometer. The barometer works, we don’t know of the thermostat does. See photos for further condition detail. We are located on Antique Row in Denver. Featuring European furniture and accessories for the mountain home. Black Forest carvings, antler furniture, antique linen for the country look. Meet our owner, Diana Neisler. Diana grew up in Heidelberg, Germany and from a young age developed an appreciation for beautiful objects having grown up studying them. When she lived in Paris, she enjoyed going to the museum every Sunday. Speaking six languages, Diana has knowledge base in European antiques with a specialized expertise in Black Forest carvings, hunting and sporting related items, antler pieces, and military. She opened her flagship boutique store on Denver’s Historic Antique Row in 2000 and her collection is only surpassed by her satisfied customers both in Colorado and online. See my other listings. For more great items!

We can only supply an EXACT quote once the item is packed and we have the exact weight and dimensions. We will take a return only if the item has been misrepresented. Add to Favorite Sellers. Txzj pxzj430 txzj34 txzj50. The item “Antique Black Forest Wood Carving Thermometer Barometer Hunt Fox Crow Paris” is in sale since Friday, April 29, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “heidelbergantiques” and is located in Denver, Colorado. This item can be shipped worldwide. Maker: Patoueille Real ANTIQUE French Barometre HOLOSTERIQUE Marine BAROMETER MADE IN FRANCE Posted on September 27, 2016 and filed under Uncategorized . ALL OFFERS ARE WEL-COME. NEGATIVE OR NEUTRAL FEEDBACK WITHOUT COMMUNICATION WILL NOT BE ALLOWED.

The item “Real ANTIQUE French Barometre HOLOSTERIQUE Marine BAROMETER MADE IN FRANCE” is in sale since Thursday, September 22, 2016. This item is in the category “Collectibles\Science & Medicine (1930-Now)\Scientific Instruments\Barometers”. The seller is “sweta4086″ and is located in MUMBAI, MAHARASHTRA. This item can be shipped worldwide. Antique English barometer Posted on September 26, 2016 and filed under Uncategorized . Beautiful carved oak cased English barometer/thermometer, circa 1890. The oak case is very well executed with profuse carving and detail. The thermometer is working and has a lovely porcelain scale. The aneroid barometer also appears to be working properly and is marked MADE IN ENGLAND and has a hand to indicate changes since the prior reading. The barometer measures 26″ tall by 10″ wide with a 5 diameter barometer dial. A lovely example of Victorian English workmanship. Auctiva Free Image Hosting. Show off your items with Auctiva’s Listing Templates.

The item “Antique English barometer” is in sale since Thursday, September 22, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “enwelch503″ and is located in Portland, Oregon. This item can be shipped to United States. Exclusive Swiss BLACK forest wood carved Bear Barometer circa 1920 Posted on September 26, 2016 and filed under Uncategorized . Exclusive Barometer Wood carved Black forest Swiss circa 1920 25cm tall and 14cm wide very detailed work found no signature on it but reminds me on the ruef brothers, if you search on them you will see the similarities. We package the items here in Belgium very well so they arrive savely without any damage! Unauthorized Duplication Prohibited. The item “Exclusive Swiss BLACK forest wood carved Bear Barometer circa 1920″ is in sale since Monday, September 26, 2016. This item is in the category “Antiques\Decorative Arts\Woodenware\Carved Figures”.

The seller is “ff-antiques” and is located in Bruxelles. This item can be shipped to North, South, or Latin America, to all countries in continental Asia, to United Kingdom, to Australia. Antique Large 1913 Presentation Aneroid Barometer By Henry Hughes & Son London Posted on September 26, 2016 and filed under Uncategorized . ORIGINAL ANTIQUE LARGE 1913 PRESENTATION ANEROID BAROMETER BY HENRY HUGHES & SON LONDON. Bought from local estate. Approx 35 1/2 tall. 10 1/2 wide at widest point. Barometer dial is approx 8. Fantastic oak case in great condition. Glass on barometer has some damage – see pics. Glass over thermometer is a bit dirty on the inside. Brass presentation plaque reads: Presented to Mr. Spence as a mark of esteem and regard by the staff of the Port Rates on Goods Office London 31st March 1913. Themometer works, not sure about Barometer – not an expert! Please see my other auctions for more estate military items. Thank you and good luck!

As required by your country’s laws, they are not charged by me and I have no responsibility toward them. Sellers: Add a FREE map to your listings. The item “ANTIQUE LARGE 1913 PRESENTATION ANEROID BAROMETER BY HENRY HUGHES & SON LONDON” is in sale since Sunday, September 25, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “aceshigh!” and is located in East Northport, New York. This item can be shipped to United States. W E Hadlock & Co. Boston Mass Early Barometer scientific Instrument Weather Posted on September 25, 2016 and filed under Uncategorized . Another great attic find in Mass! W E Hadlock & Company glass and wooden cased brass Barometer. Just found and I know little about it, except it appears in excellent condition. What you see is what is for sale……. What is the purpose of the round short brass tube in the center? The item “W E Hadlock & Co.

Boston Mass Early Barometer scientific Instrument Weather” is in sale since Friday, September 23, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “freshpickins” and is located in Waterville, Maine. This item can be shipped to United States. RARE 19 TH c ENGLISH OAK BOOT JACK AFTER GILLOWS HAND CARVED EQUESTR Posted on September 25, 2016 and filed under Uncategorized . Here we have a rare english oak Boot Jack! COndition see images 1 loss on the bottom corner of the jac and 1 on the edge of the upright, no big deal and to be expected due to it’s antiques age. This is the best example I could find on the net!! It retains a very good surface and patina. Damaged items (and packaging material) must be retained for inspection by the carrier I Sell mostly Antique and Vintage Items and it is impossible to describe all imperfections, scratches, scuffs, etc… Items with age typically display patina along with signs of use.

Be sure to view all the photos we take the time to process and display in a clear large format. I WANT YOU TO BE 100% SATISFIED….. 100% feedback for 14 years. E-bay has recently changed their feedback system where sellers can suffer penalties if anything besides a “5″ is left and you may be hurting your favorite sellers without knowing it. The item “RARE 19 TH c ENGLISH OAK BOOT JACK AFTER GILLOWS HAND CARVED EQUESTR” is in sale since Saturday, September 24, 2016. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “fje” and is located in Shelton, Connecticut. This item can be shipped to United States. July21_2014_02 Botanical Glossary - Home - References Cited An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid.

Invented in 1844 by French scientist Lucien Vidi uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. 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. This type of barometer is common in homes and in recreational boats but also used in meteorology, mostly as barograph and pressure instruments in radiosondes. Photos - British Made Shortland Barmometer in a wooden housing. Bulova was founded and incorporated as the J.

Bulova Company in 1875 by Joseph Bulova (1851  November 18, 1936), an immigrant from Bohemia. It was reincorporated under the name Bulova Watch Company in 1923, and became part of the Loews Corporation in 1979 and sold to Citizen at the end of 2007. In 1912, he launched his first plant dedicated entirely to the production of watches. Manufacturing watches at their factory in Biel (Switzerland), Bulova began a standardized mass production never seen in the world of watchmaking until then. In 1919, Joseph Bulova offered the first complete range of watches for men. The iconic visual style of his first popular advertising made its watches popular with the American public. But beyond the original style, precision and technological research also became an endless quest for Bulova. In 1920, he set up an observatory on the roof of a skyscraper to make measurements that would enable him to determine very precisely universal time.

Bulova established its operations in Woodside, New York, and Flushing, New York, where it made innovations in watchmaking, and developed a number of watchmaking tools. Its horological innovations included the Accutron watch, which used a resonating tuning fork as a means of regulating the time-keeping function. Bulova became a renowned watch company in 1923. Bulova produced the first advertisement broadcast on radio in 1926, announcing the first beep of history: «At the tone, it's eight o'clock, Bulova Watch Time», an announcement heard by millions of Americans. In 1927, Charles A. Lindbergh was the first pilot to cross the Atlantic nonstop. His crossing earned him a Bulova Watch and a check for $1000, and it became an emblem for the brand that created the model "Lone Eagle" in his likeness. Bulova claims to have been the first manufacturer to offer electric clocks beginning in 1931, but the Warren Telechron Company began selling electric clocks in 1912, 19 years prior to Bulova.

In the 1930s and 1940s, the brand was a huge success with its rectangular plated watches whose case was strongly curved to better fit the curve of the wrist. Photos - Frames left and right: A Bulova clock and barometer in a wooden housing. Center frame: Metal art - Assembly Art - spark plug body and other metal pieces shaped into a biplane. The modern foil is descended from the training weapon for the small-sword, the common sidearm of 18th century gentleman. Rapier and even longsword foils are also known to have been used, but they were very different in terms of weight and use. The foil was invented in France as a training weapon in the middle of the 18th century in order to practise fast and elegant thrust fencing. Fencers blunted the point by wrapping a foil around the blade or fastening a knob on the point ("blossom", French fleuret). In addition to practising, some fencers took away the protection and used the sharp foil for duels. German students took up that practice in academic fencing and developed the Pariser ("Parisian") thrusting small sword for the Stoßmensur ("thrusting mensur").

The target area for modern foil is said to come from a time when fencing was practised with limited safety equipment. Another factor in the target area is that foil rules are derived from a period when duelling to the death was the norm. Hence, the favoured target area is the torso, where the vital organs are. Photos - Frames left and right: A vintage fencing foil with wood handle Center frame: A metal, participant's car plaque for thre 1997 Vancouver Whistler All British Car Run. Barometer Explained Barometer Barometer Explained A barometer is a scientific instrument used in meteorology to measure atmospheric pressure . Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface trough s, high pressure systems and frontal boundaries. Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from place to place matching the atmospheric pressure to the corresponding altitude , while a barometer is kept stationary and measures subtle pressure changes caused by weather.

The main exception to this is ship s at sea, which can use a barometer because their elevation does not change. Due to the presence of weather systems, aircraft altimeter s may need to be adjusted as they fly between regions of varying normalized atmospheric pressure. History Although Evangelista Torricelli is universally credited with inventing the barometer in 1643, [1] [2] [3] historical documentation also suggests Gasparo Berti , an Italian mathematician and astronomer, unintentionally built a water barometer sometime between 1640 and 1643. [1] [4] French scientist and philosopher René Descartes described the design of an experiment to determine atmospheric pressure as early as 1631, but there is no evidence that he built a working barometer at that time. [1] On July 27, 1630, Giovanni Battista Baliani wrote a letter to Galileo Galilei explaining an experiment he had made in which a siphon , led over a hill about twenty-one meters high, failed to work.

Galileo responded with an explanation of the phenomenon: he proposed that it was the power of a vacuum that held the water up, and at a certain height the amount of water simply became too much and the force could not hold any more, like a cord that can support only so much weight. [5] [6] This was a restatement of the theory of horror vacui ("nature abhors a vacuum"), which dates to Aristotle , and which Galileo restated as resistenza del vacuo. Galileo's ideas reached Rome in December 1638 in his Discorsi. Raffaele Magiotti and Gasparo Berti were excited by these ideas, and decided to seek a better way to attempt to produce a vacuum than with a siphon. Magiotti devised such an experiment, and sometime between 1639 and 1641, Berti (with Magiotti, Athanasius Kircher and Niccolò Zucchi present) carried it out. [6] Four accounts of Berti's experiment exist, but a simple model of his experiment consisted of filling with water a long tube that had both ends plugged, then standing the tube in a basin already full of water.

The bottom end of the tube was opened, and water that had been inside of it poured out into the basin. However, only part of the water in the tube flowed out, and the level of the water inside the tube stayed at an exact level, which happened to be 10.3 m, the same height Baliani and Galileo had observed that was limited by the siphon. What was most important about this experiment was that the lowering water had left a space above it in the tube which had no intermediate contact with air to fill it up. This seemed to suggest the possibility of a vacuum existing in the space above the water. [6] Torricelli, a friend and student of Galileo, interpreted the results of the experiments in a novel way. He proposed that the weight of the atmosphere, not an attracting force of the vacuum, held the water in the tube. In a letter to Michelangelo Ricci in 1644 concerning the experiments, he wrote: Many have said that a vacuum does not exist, others that it does exist in spite of the repugnance of nature and with difficulty; I know of no one who has said that it exists without difficulty and without a resistance from nature.

I argued thus: If there can be found a manifest cause from which the resistance can be derived which is felt if we try to make a vacuum, it seems to me foolish to try to attribute to vacuum those operations which follow evidently from some other cause; and so by making some very easy calculations, I found that the cause assigned by me (that is, the weight of the atmosphere) ought by itself alone to offer a greater resistance than it does when we try to produce a vacuum. [7] It was traditionally thought (especially by the Aristotelians) that the air did not have lateral weight: that is, that the kilometers of air above the surface did not exert any weight on the bodies below it. Even Galileo had accepted the weightlessness of air as a simple truth. Torricelli questioned that assumption, and instead proposed that air had weight and that it was the latter (not the attracting force of the vacuum) which held (or rather, pushed) up the column of water. He thought that the level the water stayed at (c.

10.3 m) was reflective of the force of the air's weight pushing on it (specifically, pushing on the water in the basin and thus limiting how much water can fall from the tube into it). In other words, he viewed the barometer as a balance, an instrument for measurement (as opposed to merely being an instrument to create a vacuum), and because he was the first to view it this way, he is traditionally considered the inventor of the barometer (in the sense in which we use the term now). [6] Because of rumors circulating in Torricelli's gossipy Italian neighborhood, which included that he was engaged in some form of sorcery or witchcraft, Torricelli realized he had to keep his experiment secret to avoid the risk of being arrested. He needed to use a liquid that was heavier than water, and from his previous association and suggestions by Galileo, he deduced by using mercury , a shorter tube could be used. With mercury, which is about 14 times heavier than water, a tube only 80 cm was now needed, not 10.5 m.

[8] In 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 experiment 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 in 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 vapors would mean more pushing down on the liquid column). Pascal performed the experiment publicly, inviting the Aristotelians to predict the outcome beforehand. The Aristotelians predicted the wine would stand lower. It did not. [6] However, 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 air 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 crucial 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 it to 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 carried out the experiment, and found that Pascal's predictions had been correct. The mercury barometer stood lower the higher one went. [6] Types Water-based barometers The concept that decreasing atmospheric pressure predicts stormy weather, postulated by Lucien Vidi , provides the theoretical basis for a weather prediction device called a "storm 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 Torricelli ). The French name, le baromètre Liègeois, is used by some English speakers. [9] This name reflects the origins of many early weather glasses - the glass blowers of Liège , Belgium . [9] [10] 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. [11] Mercury barometers A mercury barometer has a glass tube closed at one end with an open mercury-filled reservoir at the base. The weight of the mercury creates a vacuum in the top of the tube known as Torricellian vacuum. Mercury in the tube adjusts until the weight of the mercury column 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. 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 atmosphere . [1] He wrote: "We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight". [12] The 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 height in the vertical column. Typically, atmospheric pressure is measured between and of Hg. One atmosphere (1 atm) is equivalent to 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. Fitzroy barometers combine the standard mercury barometer with a thermometer, as well as a guide of how to interpret pressure changes.

Fortin barometers use a variable displacement mercury cistern, usually constructed with a thumbscrew pressing on a leather diaphragm bottom. This compensates for displacement 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. 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. On 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. 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 ~12.4 m for the oil column height; expected excursions are in the range of ±0.4 m over the course 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 maximize the oil column height. [13] Aneroid barometers See also: Barograph . An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid . Invented in 1844 by French scientist Lucien Vidi , [14] the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper . 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.

This type of barometer is common in homes and in recreational boat s, as well as small aircraft. It is also used in meteorology , mostly in barograph s and as a pressure instrument in radiosonde s. Barographs A barograph records a graph of some atmospheric pressure and uses an aneroid barometer mechanism to move a needle on a smoked foil or to move a pen upon paper, both of which are attached to a drum moved by clockwork. [15] MEMS Barometers Microelectromechanical systems (or MEMS) barometers are extremely small devices between 1 and 100 micrometres in size (i.e. 0.001 to 0.1 mm). They are created via photolithography or photochemical machining . Typical applications include miniaturized weather stations, electronic barometers and altimeters. [16] More unusual barometers 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, [17] work only in a certain temperature range, achieved in warmer climates. A barometer can also be found in smartphones such as the Samsung Galaxy Nexus , [18] Samsung Galaxy S3-S6, Motorola Xoom and Apple iPhone 6 smartphones, based on MEMS and piezoresistive pressure-sensing technologies. [19] [20] Inclusion of barometers on smartphones was originally intended to provide a faster GPS lock. [21] However, 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 to determining a user's elevation, but also suggest that several pitfalls must first be overcome. [22] Applications See also: Surface weather analysis and Weather forecasting . Barometric pressure and the pressure tendency (the change of pressure over time) have been used in weather forecasting since the late 19th century. [23] When used in combination with wind observations, reasonably accurate short-term forecasts can be made.

[24] 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, give a contour map showing areas of high and low pressure. [25] 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 sometimes precipitation . [26] The larger the change in pressure, especially if more than 3.5 hPa, the greater the change in weather that can be expected. If the pressure drop is rapid, a low pressure system is approaching, and there is a greater chance of rain. Rapid pressure rises , such as in the wake of a cold front , are associated with improving weather conditions, such as clearing skies. [27] With falling air pressure, gases trapped within the coal in deep mines can escape more freely. Thus low pressure increases the risk of firedamp accumulating. Collieries therefore keep track of the pressure.

In the case of the Trimdon Grange colliery disaster of 1882 the mines inspector drew attention to the records and in the report stated "the conditions of atmosphere and temperature may be taken to have reached a dangerous point". Aneroid barometers are used in scuba diving . A Submersible pressure gauge is used to keep track of the contents of the diver's air tank. Another gauge is used to measure the hydrostatic pressure, usually expressed as a depth of sea water. Either or both gauges may be replaced with electronic variants or a dive computer. Compensations Temperature The density of mercury will change with temperature, so a reading must be adjusted for the temperature of the instrument. For this purpose a mercury thermometer is usually mounted on the instrument. Temperature compensation of an aneroid barometer is accomplished by including a bi-metal element in the mechanical linkages. Aneroid barometers sold for domestic use typically have no compensation under the assumption that they will be used within a controlled room temperature range. Altitude As the air pressure decreases at altitude s above sea level (and increases below sea level) the uncorrected reading of the barometer will depend on its location.

The reading is then adjusted to an equivalent sea-level pressure for purposes of reporting. For example, if a barometer located at sea level and under fair weather conditions is moved to an altitude of 1,000 feet (305 m), about 1 inch of mercury (~35 hPa) must be added on to the reading. The barometer readings at the two locations should be the same if there are negligible changes in time, horizontal distance, and temperature. If this were not done, there would be a false indication of an approaching storm at the higher elevation. Aneroid barometers have a mechanical adjustment that allows the equivalent sea level pressure to be read directly and without further adjustment if the instrument is not moved to a different altitude. Setting an aneroid barometer is similar to setting an analog clock that is not at the correct time. Its dial is rotated so that the current atmospheric pressure from a known accurate and nearby barometer (such as the local weather station ) is displayed. No calculation is needed, as the source barometer reading has already been converted to equivalent sea-level pressure, and this is transferred to the barometer being set—regardless of its altitude.

Though somewhat rare, a few aneroid barometers intended for monitoring the weather are calibrated to manually adjust for altitude. In this case, knowing either the altitude or the current atmospheric pressure would be sufficient for future accurate readings. The table below shows examples for three locations in the city of San Francisco , California . Note the corrected barometer readings are identical, and based on equivalent sea-level pressure. (Assume a temperature of 15 °C.) Location [28] When atmospheric pressure is measured by a barometer, the pressure is also referred to as the "barometric pressure". Assume a barometer with a cross-sectional area A, a height h, filled with mercury from the bottom at Point B to the top at Point C. The pressure at the bottom of the barometer, Point B, is equal to the atmospheric pressure. The pressure at the very top, Point C, can be taken as zero because there is only mercury vapor above this point and its pressure is very low relative to the atmospheric pressure.

Therefore, one can find the atmospheric pressure using the barometer and this equation: Patm = ρgh where ρ is the density of mercury, g is the gravitational acceleration, and h is the height of the mercury column above the free surface area. The physical dimensions (length of tube and cross-sectional area of the tube) of the barometer itself have no effect on the height of the fluid column in the tube. In thermodynamic calculations, a commonly used pressure unit is the "standard atmosphere". This is the pressure resulting from a column of mercury of 760 mm in height at 0 °C. For the density of mercury, use ρHg = 13,595 kg/m3 and for gravitational acceleration use g = 9.807 m/s2. If water were used (instead of mercury) to meet the standard atmospheric pressure, a water column of roughly 10.3 m (33.8 ft) would be needed.

Standard atmospheric pressure as a function of elevation: Note: 1 torr = 133.3 Pa = 0.03937 In Hg Patm Vintage C PLATH Aneroid Bulkhead Barometer Nautical Antiques & Marine Art at Land and Sea Collection™ Dive Helmets, Ship Models, Sextants Vintage C PLATH Aneroid Bulkhead Barometer Vintage C PLATH Aneroid Bulkhead Barometer Maximum diameter 8 1/2" Dia. dial 6" Height 2 3/4" Weight 3 pounds Presented is a very rare C. Plath aneroid barometer that is stamped with the number 2165 on the back of its hardwood case. It is very different from many other barometers of this type available on today's market because of its high quality C. Plath mechanism, which results in extremely accurate readings. Plath for years has been a maker of instruments used for marine navigation and continues in business today. Our tests show that it reads very close to the data reported for this location at the same time. PROVENANCE: It has been in the same family for the past 50+ years.

A descendent recalls that it was shipped to an Oregon antique auction house in the 1960s or early 1970s as part of a container of antiques from the United Kingdom and Europe where it was purchased. It was described as a German barometer used on a ship. Aneroid barometers measure pressure by a method that does not use a liquid. Invented in 1844 by French scientist Lucien Vidi, the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. The evacuated capsule 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.

This type of barometer is common in homes and in recreational boats, as well as small aircraft. It is also used in meteorology, mostly in barographs and as a pressure instrument in radiosondes. credit wikipedia Movement of the Plath android barometer. This is the only example of this barometer that we have been able to find. Our research has included a review of the internet and of our C. Plath reference works including self-published books of the company's history through its 1st 150 years. Plath sextants were considered to be the Rolls Royce of celestial navigation instruments and we consider this device to be of the same caliber. Viewing the barometer from the left. Note the thick beveled crystal. CONDITION: There is little fault to find except to note the normal marks of age and the darkening of the varnish with time. There are two mounting tabs missing from the back. The instrument reads very closely to the reported data in this area. There is an adjustment screw on the back for setting the pressure. Showing the pointers and the high quality print Back of case showing two missing tabs and No. 2165 at the top C.

PLATH COMPANY HISTORY: In brief, Carl Plath started manufacturing sextants, in addition to other nautical products, in Hamburg Germany in 1862 though the purchase of the David Filby instrument company though the company's origin dates back to 1837. As a result WW II, C.Plath was dismantled completely by the occupation forces. Around 1950, various prohibitions were lifted, and C. Plath was allowed to begin production again of sextants and other nautical instruments. Also in 1949,C.Plath was offered a gyrocompass patent and in 1951 the first gyrocompass designed to this patent was presented to the public. C.Plath progressed from the role of instrument maker to that of a modern marine navigation equipment manufacturer. In the following years the product range was expanded by many more modern designs such as autopilots, speed logs, radio direction finders, etc. In 1962 C.Plath was acquired by Litton Industries, a large American concern.The C.Plath North American Division was set up in 1978 in College Park near Washington.

1996 saw the introduction of the world's first fiber-optic solid-state gyrocompass by C.Plath. The first ever gyrocompass with no moving parts. Sperry Marine was formed in 1997 with the combination of C.Plath, Decca Marine and Sperry Marine with more organizational changes yet to come. After 163 years, C.Plath changes its name to Sperry Marine in May 2000. In 2001 Sperry Marine becomes part of the Northrop Grumman Corporation. OUR QUALIFICATIONS: We are one of the few company's still selling navigation instruments that know anything about them. For purposes of judging whether Joel's opinion counts, he was the editor of the chapter on sextants of the 1977 Edition of "Bowditch", The American Practical Navigator, NAVPUB 9; a member of the U.S.

Naval Academy Navigation Symposium, 1975 -1978; the author of a book on marine sextants, Cornell Maritime Press,1975, and the founding president of Nautech Maritime Corporation which partnered with Tamaya of Japan in the introduction of the MS 733 Spica, the MS 833, Jupiter, MS 933 Venus sextants and the famous NC-2 navigation computer, in the U.S. market. Joel is a retired Master Upon Oceans, and held a U.S. Navy "D" Qualification as a Senior Skipper - Oceans. For six years he was a Varsity Offshore Sailing Team Coach at the U.S. Naval Academy. Some of his memberships have included the: Association of Naval Aviation, Silver Wings, The Tailhook Association, Naval Academy Sailing Squadron, McCampbell's Aces Squadron, Naval Historical Foundation, and the Naval Order of the United States. STANDARD FLAT RATE SHIPPING, INSURANCE & PACKING to 48 contiguous States, $40.00.

OUR UNCONDITIONAL NO NONSENSE GUARANTEE: If not completely satisfied with your purchase it may be returned within five days of receipt in its original packaging if without damage. Return items must be insured for their full value. Only a prior email authorization from us for the return is required. Shipping charges are included in this offer within the continental United States if an error is due to our fault. COUNTRIES SERVED: International buyers welcome, but inquire first. We have satisfied customers in Argentina, Australia, Austria, Belgium, Bermuda, British Virgin Islands, Canada, Chile, Republic of China, Czech Republic, Democratic Republic of Congo, Denmark, Estonia, England, France, Germany, Greece, Holland, Hong Kong, Hungary, Iceland, Indonesia, Ireland, Israel, Italy, Japan, Kuwait, Latvia, Luxembourg, Malaysia, Martinique, Mexico, New Hebrides (Vanuatu), New Zealand, Nigeria, Norway, Nova Scotia, Panama, Philippines, Poland, Portugal, Puerto Rico, Romania, Russia, Saudi Arabia, Scotland, Singapore, South Africa, Spain, St. Maarten, Sweden, Switzerland, Thailand, Turkey, United Arab Emirates, Vanuatu (New Hebrides), USVI and the Eastern Caribbean.

ACCEPTED FORMS OF PAYMENT are Bank wire transfer, cashier's check, or personal check in which case the item will be held until cleared. Our prices are quoted net to seller, but credit cards may be accepted through PayPal for verified members by special arrangement at an additional charge. Overseas terms are different. Copyright 2015 by Land And Sea Collection™. All Rights Reserved. Barometer | Open Access articles | Open Access journals | Conference Proceedings | Editors | Authors | Reviewers | scientific events e A barometer is a scientific instrument used in meteorology to measure atmospheric pressure . Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs , high pressure systems and frontal boundaries. Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from place to place matching the atmospheric pressure to the corresponding altitude , while a barometer is kept stationary and measures subtle pressure changes caused by weather. The main exception to this is ships at sea, which can use a barometer because their elevation does not change.

Due to the presence of weather systems, aircraft altimeters may need to be adjusted as they fly between regions of varying normalized atmospheric pressure. Contents 9 Further reading History Although Evangelista Torricelli is universally credited with inventing the barometer in 1643, [1] [2] [3] historical documentation also suggests Gasparo Berti , an Italian mathematician and astronomer, unintentionally built a water barometer sometime between 1640 and 1643. [1] [4] French scientist and philosopher René Descartes described the design of an experiment to determine atmospheric pressure as early as 1631, but there is no evidence that he built a working barometer at that time. [1] On July 27, 1630, Giovanni Battista Baliani wrote a letter to Galileo Galilei explaining an experiment he had made in which a siphon , led over a hill about twenty-one meters high, failed to work.

Galileo responded with an explanation of the phenomenon: he proposed that it was the power of a vacuum that held the water up, and at a certain height the amount of water simply became too much and the force could not hold any more, like a cord that can support only so much weight. [5] [6] This was a restatement of the theory of horror vacui ("nature abhors a vacuum"), which dates to Aristotle , and which Galileo restated as resistenza del vacuo. Galileo's ideas reached Rome in December 1638 in his Discorsi. Raffaele Magiotti and Gasparo Berti were excited by these ideas, and decided to seek a better way to attempt to produce a vacuum than with a siphon. Magiotti devised such an experiment, and sometime between 1639 and 1641, Berti (with Magiotti, Athanasius Kircher and Niccolò Zucchi present) carried it out. [6] Four accounts of Berti's experiment exist, but a simple model of his experiment consisted of filling with water a long tube that had both ends plugged, then standing the tube in a basin already full of water.

The bottom end of the tube was opened, and water that had been inside of it poured out into the basin. However, only part of the water in the tube flowed out, and the level of the water inside the tube stayed at an exact level, which happened to be 10.3 m,[ citation needed ] the same height Baliani and Galileo had observed that was limited by the siphon. What was most important about this experiment was that the lowering water had left a space above it in the tube which had no intermediate contact with air to fill it up. This seemed to suggest the possibility of a vacuum existing in the space above the water. [6] Torricelli, a friend and student of Galileo, interpreted the results of the experiments in a novel way. He proposed that the weight of the atmosphere, not an attracting force of the vacuum, held the water in the tube. In a letter to Michelangelo Ricci in 1644 concerning the experiments, he wrote: Many have said that a vacuum does not exist, others that it does exist in spite of the repugnance of nature and with difficulty; I know of no one who has said that it exists without difficulty and without a resistance from nature.

I argued thus: If there can be found a manifest cause from which the resistance can be derived which is felt if we try to make a vacuum, it seems to me foolish to try to attribute to vacuum those operations which follow evidently from some other cause; and so by making some very easy calculations, I found that the cause assigned by me (that is, the weight of the atmosphere) ought by itself alone to offer a greater resistance than it does when we try to produce a vacuum. [7] It was traditionally thought (especially by the Aristotelians) that the air did not have lateral weight: that is, that the kilometers of air above the surface did not exert any weight on the bodies below it. Even Galileo had accepted the weightlessness of air as a simple truth. Torricelli questioned that assumption, and instead proposed that air had weight and that it was the latter (not the attracting force of the vacuum) which held (or rather, pushed) up the column of water. He thought that the level the water stayed at (c.

10.3 m) was reflective of the force of the air's weight pushing on it (specifically, pushing on the water in the basin and thus limiting how much water can fall from the tube into it). In other words, he viewed the barometer as a balance, an instrument for measurement (as opposed to merely being an instrument to create a vacuum), and because he was the first to view it this way, he is traditionally considered the inventor of the barometer (in the sense in which we use the term now). [6] Because of rumors circulating in Torricelli's gossipy Italian neighborhood, which included that he was engaged in some form of sorcery or witchcraft, Torricelli realized he had to keep his experiment secret to avoid the risk of being arrested. He needed to use a liquid that was heavier than water, and from his previous association and suggestions by Galileo, he deduced by using mercury , a shorter tube could be used. With mercury, then called "quicksilver", which is about 14 times heavier than water, a tube only 80 cm was now needed, not 10.5 m.

[8] In 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 experiment 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 in 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 vapors would mean more pushing down on the liquid column). Pascal performed the experiment publicly, inviting the Aristotelians to predict the outcome beforehand. The Aristotelians predicted the wine would stand lower. It did not. [6] However, 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 air 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 crucial 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 it to 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 carried out the experiment, and found that Pascal's predictions had been correct. The mercury barometer stood lower the higher one went. [6] Types File:Barometer Goethe 01.jpg 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 "storm 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 Torricelli ). The French name, le baromètre Liégeois, is used by some English speakers. [9] This name reflects the origins of many early weather glasses - the glass blowers of Liége , Belgium .

[9] [10] 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. [11] Mercury barometers A 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 vacuum 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 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. File:MercuryBarometer.svg Schematic drawing of a simple mercury barometer with vertical 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 atmosphere . [1] He wrote: "We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight". [12] The 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 height in the vertical column. Typically, atmospheric pressure is measured between 26.5 to 31.5 inches of Hg. One atmosphere (1 atm) is equivalent to 29.92 inches 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. Fitzroy barometers combine the standard mercury barometer with a thermometer, as well as a guide of how to interpret pressure changes. Fortin barometers use a variable displacement mercury cistern, usually constructed with a thumbscrew pressing on a leather diaphragm bottom. This compensates for displacement 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. 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. On 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.

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 ~12.4 m for the oil column height; expected excursions are in the range of ±0.4 m over the course 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 maximize the oil column height. [13] Aneroid barometers File:Barometer.JPG Modern aneroid barometer An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid . Invented in 1844 by French scientist Lucien Vidi , [14] the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper . 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. This type of barometer is common in homes and in recreational boats , as well as small aircraft. It is also used in meteorology , mostly in barographs and as a pressure instrument in radiosondes . Barographs A barograph records a graph of some atmospheric pressure and uses an aneroid barometer mechanism to move a needle on a smoked foil or to move a pen upon paper, both of which are attached to a drum moved by clockwork. [15] MEMS Barometers Microelectromechanical systems (or MEMS) barometers are extremely small devices between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm).

They are created via photolithography or photochemical machining . Typical applications include miniaturized weather stations, electronic barometers and altimeters. [16] More unusual barometers The Galaxy Nexus has a built-in barometer [17] 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, [18] work only in a certain temperature range, achieved in warmer climates. A barometer can also be found in smartphones such as the Samsung Galaxy Nexus , [19] Samsung Galaxy S3-S6, Motorola Xoom and Apple iPhone 6 smartphones, to provide a faster GPS lock. [20] Applications File:Barograph 01.jpg Analogue recording Barograph using five stacked aneroid barometer cells. Using barometric pressure and the pressure tendency (the change of pressure over time) has been used in weather forecasting since the late 19th century. [21] When used in combination with wind observations, reasonably accurate short-term forecasts can be made.

[22] 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. [23] 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 . [24] 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 . Rapid pressure rises , such as in the wake of a cold front , are associated with improving weather conditions, such as clearing skies. [25] Compensations Temperature The density of mercury will change with temperature, so a reading must be adjusted for the temperature of the instrument. For this purpose a mercury thermometer is usually mounted on the instrument.

Temperature compensation of an aneroid barometer is accomplished by including a bi-metal element in the mechanical linkages. Aneroid barometers sold for domestic use typically have no compensation under the assumption that they will be used within a controlled room temperature range. Altitude As the air pressure will be decreased at altitudes above sea level (and increased below sea level) the uncorrected reading of the barometer will be dependent upon its location. This pressure measurement is then converted to an equivalent sea-level pressure for purposes of reporting. For example, if a barometer located at sea level and under fair weather conditions is moved to an altitude of 1,000 feet (305 m), about 1 inch of mercury (~35 hPa) must be added on to the reading. The barometer readings at the two locations should be the same if there are negligible changes in time, horizontal distance, and temperature. If this were not done, there would be a false indication of an approaching storm at the higher elevation. Aneroid barometers have a mechanical adjustment that allows the equivalent sea level pressure to be read directly and without further adjustment if the instrument is not moved to a different altitude.

Setting an aneroid barometer is similar to setting an analog clock that is not at the correct time. Its dial is rotated so that the current atmospheric pressure from a known accurate and nearby barometer (such as the local weather station ) is displayed. No calculation is needed, as the source barometer reading has already been converted to equivalent sea-level pressure, and this is transferred to the barometer being set—regardless of its altitude. Though somewhat rare, a few aneroid barometers intended for monitoring the weather are calibrated to manually adjust for altitude. In this case, knowing either the altitude or the current atmospheric pressure would be sufficient for future accurate readings. The table below shows examples for three locations in the city of San Francisco , California . Note the corrected barometer readings are identical, and based on equivalent sea-level pressure. (Assume a temperature of 15 °C.) Location [26] When atmospheric pressure is measured by a barometer, the pressure is also referred to as the barometric pressure. Assume a barometer with a cross-sectional area, A, a height, h, filled with mercury from the bottom at Point B to the top at Point C.

The pressure at the bottom of the barometer, Point B, is equal to the atmospheric pressure. The pressure at the very top, Point C, can be taken as zero because there is only mercury vapor above this point and its pressure is very low relative to the atmospheric pressure. Therefore, one can find the atmospheric pressure using the barometer and this equation: Patm = ρgh where ρ is the density of mercury, g is the gravitational acceleration, and h is the height of the mercury column above the free surface area. Note that the physical dimensions (length of tube and cross-sectional area of the tube) of the barometer itself have no effect on the height of the fluid column in the tube. In thermodynamic calculations, a commonly used pressure unit is the standard atmosphere. This is the pressure resulting from a column of mercury of 760mm in height at 0 °C. For the density of mercury, use ρHg = 13,595 kg/m3 and for gravitational acceleration use g = 9.807 m/s2.

If water were used (instead of mercury) to meet the standard atmospheric pressure, a water column of roughly 10.3 m (33.8 ft) would be needed. Standard atmospheric pressure as a function of elevation. Note: 1 torr = 133.3 Pa = 0.03937 In Hg Patm Barometer, walnut mount, circa 1900 Barometer, walnut mount, circa 1900 Be the first to know about the latest online auctions. Please enter a valid email address (name@host.com) Sign Up » PS: We value your privacy Thank you! Invaluable cannot guarantee the accuracy of translations through Google Translate and disclaims any responsibility for inaccurate translations. Show translation options Log in or create account for price data » Description: Category: Furniture Description: A barometer with a walnut mount. The barometer has a white background, the hands are gold and black, and the scripts are French in black and red. The words go from stormy to very dry in their description of the current weather prediction. Below the barometer is a thermometer set on brass.

Condition Report: A 3/4 inch loss in the base below the thermometer, light patination of the brass, minor wear over all. Notes: An aneroid barometer is an instrument for measuring pressure as a method that does not involve liquid. Invented in 1844 by French scientist Lucien Vidi, the aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. 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. This type of barometer is common in homes and in recreational boats, as well as small aircraft.

It is also used in meteorology, mostly in barographs and as a pressure instrument in radiosondes. Provenance: n/a

Question: Which type of barometer that does not involve liquid was invented by Lucien Vidi in 1844?
Answer: ANEROID