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Encyclopedia > Atmosphere (unit)

Standard atmosphere (symbol: atm) is a unit of pressure. Standard atmosphere is a non-SI unit that is internationally recognized. The 10th Conférence Générale des Poids et Mesures (10th CGPM) adopted standard atmosphere for general use and affirmed its definition of being precisely equal to 1,013,250 dynes per cm2 (101,325 Pa). This value is intended to represent the mean atmospheric pressure at mean sea level at the latitude of Paris, France, and as a practical matter, truly reflects the mean sea level pressure for many of the industrialized nations (those with latitudes similar to Paris). The former Weights and Measures office in Middlesex, England. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... In physics, the dyne is a unit of force specified in the centimetre-gram-second (cgs) system of units, symbol dyn. One dyne is equal to exactly 10-5 newtons. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... City flag City coat of arms Motto: Fluctuat nec mergitur (Latin: Tossed by the waves, she does not sink) Paris Eiffel tower as seen from the esplanade du Trocadéro. ...


Equivalencies

A pressure of 1 atm can also be stated as:

≡1.013 25 bar
≡101.325 kPa
≡1013.25 millibars (mbar, also mb) or hectopascals (hPa)
≡760 torr [B]
≈760.001 mm-Hg, 0°C, subject to revision as more precise measurements of mercury’s density become available [B, C]
≈29.9213 in-Hg, 0°C, subject to revision as more precise measurements of mercury’s density become available [C]
≈1.033 227 452 799 886 kg-force/cm²
≈1.033 227 452 799 886 technical atmosphere
≈1033.227 452 799 886 cm–H₂O, 4°C [A]
≈406.782 461 732 2385 in–H₂O, 4°C [A]
≈14.695 948 775 5134 pounds-force per square inch (psi)
≈2116.216 623 673 94 pounds-force per square foot (psf)
A This is the customarily-accepted value for cm–H₂O, 4°C. It is precisely the product of 1 kg-force per square centimeter (one technical atmosphere) times 1.013 25 (bar/atmosphere) divided by 0.980 665 (one gram-force). It is not accepted practice to define the value for water column based on a true physical realization of water (which would be 99.997 495% of this value because the true maximum density of Vienna Standard Mean Ocean Water is 0.999 974 95 kg/l at 3.984°C). Also, this “physical realization” would still ignore the 8.285 cm–H2O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3.984°C.
B Torr and mm-Hg, 0°C are often taken to be identical. For most practical purposes (to 5 significant digits), they are interchangeable.
C NIST value of 13.595 078(5) g/ml assumed for the density of Hg at 0°C

The bar (symbol bar) and the millibar (symbol mbar, also mb) are units of pressure. ... The pascal (symbol Pa) is the SI unit of pressure. ... A millibar (mbar, also mb) is 1/1000th of a bar, a unit for measurement of pressure. ... The pascal (symbol Pa) is the SI unit of pressure. ... For the standard botanical author abbreviation Torr. ... A technical atmosphere (symbol: at) is a non-SI unit of pressure equal to 1 kilogram-force per square centimeter, i. ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in2) is a non-SI unit of pressure based on avoirdupois units. ... VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. ... As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ...

Applications

In chemistry, standard temperature and pressure (STP) is defined as a reference temperature of 0°C (273.15 K) and pressure of 101.325 kPa (1 atm). In 1990, the standard pressure was changed from 1atm to an absolute pressure of 100kPa. This article or section includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... In chemistry and other sciences, STP or standard temperature and pressure is a standard set of conditions for experimental measurements, to enable comparisons to be made between sets of data. ... The degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. ... The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero—the lowest possible temperature where nothing could be colder and no heat energy remains in a substance—is defined as zero kelvin (0 K). ... The pascal (symbol Pa) is the SI unit of pressure. ...


In the United Kingdom, scuba divers and others often use the word atmosphere loosely to mean 1 bar (1000 millibars, or 100 000 Pa). Early ideas of autonomous under-water systems appear in Twenty Thousand Leagues Under the Sea Scuba Diving is the use of independent breathing equipment to stay underwater for long periods for recreational diving and professional diving. ... The bar (symbol bar) and the millibar (symbol mbar, also mb) are units of pressure. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...


The unit technical atmosphere (at) is roughly equal to the gauge pressure under 10 m of water; 1 at = 98066.5 Pa. A technical atmosphere (symbol: at) is a non-SI unit of pressure equal to 1 kilogram-force per square centimeter, i. ... The metre, or meter (U.S.), is a measure of length. ...

Pressure Units
 
Pascal
(Pa)

Bar
(bar)
Technical atmosphere
(at)

Atmosphere
(atm)

Torr
(mmHg)
Pound-force per
square inch

(psi)
1 Pa ≡ 1 N/m² 10−5 10.197×10−6 9.8692×10−6 7.5006×10−3 145.04×10−6
1 bar 100 000 ≡ 106 dyn/cm² 1.0197 0.98692 750.06 14.504
1 at 98 066.5 0.980665 ≡ 1 kgf/cm² 0.96784 735.56 14.223
1 atm 101 325 1.01325 1.0332 ≡ 1 atm 760 14.696
1 torr 133.322 1.3332×10−3 1.3595×10−3 1.3158×10−3 ≡ 1 mmHg 19.337×10−3
1 psi 6 894.76 68.948×10−3 70.307×10−3 68.046×10−3 51.715 ≡ 1 lbf/in²

Example reading: 1 Pa = 1 N/m²  = 10−5 bar  = 10.197×10−6 at  = 9.8692×10−6 atm ....etc.
Note: mmHg is an abbreviation for millimetres of mercury. The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... The bar (symbol bar) and the millibar (symbol mbar, also mb) are units of pressure. ... A technical atmosphere (symbol: at) is a non-SI unit of pressure equal to 1 kilogram-force per square centimeter, i. ... For the standard botanical author abbreviation Torr. ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in2) is a non-SI unit of pressure based on avoirdupois units. ... The newton (symbol: N) is the SI unit of force. ... In physics, the dyne is a unit of force specified in the centimetre-gram-second (cgs) system of units, symbol dyn. One dyne is equal to exactly 10-5 newtons. ... The deprecated unit kilogram-force (kgf) or kilopond (kp) is the force exerted by one kilogram of mass in standard Earth gravity (defined as exactly 9. ... For the standard botanical author abbreviation Torr. ... The pound-force is a non-SI unit of force or weight (properly abbreviated lbf or lbf). The pound-force is equal to a mass of one pound multiplied by the standard acceleration due to gravity on Earth (which is defined as exactly 9. ...


  Results from FactBites:
 
91.06.04: Earth’s Changing Atmosphere (5852 words)
The purpose of this unit is to investigate the Earth’s changing atmosphere.
The gas in an atmosphere is held to the planet’s surface by gravity, that natural force or pull toward the center of the planet.
The troposphere is the layer of the atmosphere extending from Earth’s surface to an altitude of 10 to 16 km.
  More results at FactBites »

 
 

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