outside the usa what units are used to measure atmospheric pressure
Pressure measurement


absolute pressure in the tire is essentially unchanged. Using atmospheric pressure as reference is usually signified by a "g" for gauge after the pressure unit, e.g. 70 psig, which means that the pressure measured is the total pressure minus atmospheric pressure. There are two types of gauge reference pressure: vented gauge (vg) and sealed gauge (sg). A vented-gauge pressure transmitter, for example, allows the outside air pressure to be exposed to the negative side of the pressure-sensing diaphragm, through a vented
20483550
Useful conversions and formulas for air dispersion modeling


meters altitude A normal cubic meter (Nm³ ) is the metric expression of gas volume at standard conditions and it is usually ("but not always") defined as being measured at 0 °C and 1 atmosphere of pressure. A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is often ("but not always") defined as being measured at 60 °F and 1 atmosphere of pressure. There are other definitions of standard gas conditions used in the USA besides 60
9086656
Absolute scale


or lighting construction (where the relative pressure of the atmosphere is inconsequential), and are measured in units of "atmospheres" or torr. Barometers do measure absolute pressure by holding a vacuum at the top of the mercury column or one side of a diaphragm, but that vacuum is awkward to achieve and maintain. Thus, while the general public may be familiar with measurements of absolute pressure from weather forecasts, most pressures such as tire pressures and water pressures are measured relative to atmospheric pressure using cheaper and simpler pressure gauges.
3569490
Pressure measurement


chamber pressure gauges. Both msw and fsw are measured relative to normal atmospheric pressure. In vacuum systems, the units torr (millimeter of mercury), micron (micrometer of mercury), and inch of mercury (inHg) are most commonly used. Torr and micron usually indicates an absolute pressure, while inHg usually indicates a gauge pressure. Atmospheric pressures are usually stated using hectopascal (hPa), kilopascal (kPa), millibar (mbar) or atmospheres (atm). In American and Canadian engineering, stress is often
20483559
Pressure reference system


Pressure reference system (PRS) is an enhancement of the inertial reference system and attitude and heading reference system designed to provide position angles measurements which are stable in time and do not suffer from long term drift caused by the sensor imperfections. The measurement system uses behavior of the International Standard Atmosphere where atmospheric pressure descends with increasing altitude and two pairs of measurement units. Each pair measures pressure at two different positions that are mechanically connected with known distance between units, e.g. the units are mounted at the tips of the wing. In
19180537
Metre sea water


psi. The msw and fsw are the conventional units for measurement of diver pressure exposure used in decompression tables and the unit of calibration for pneumofathometers and hyperbaric chamber pressure gauges. One atmosphere is approximately equal to 33 feet of sea water or 14.7 psi, which gives 4.9/11 or about 0.445 psi per foot. Atmospheric pressure may be considered constant at sea level, and minor fluctuations caused by the weather are usually ignored. Pressures measured in fsw and msw are gauge pressure, relative to the surface pressure of 1 atm absolute, except
5213488
Atmospheric pressure


approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. Pressure measures force per unit area, with SI units of Pascals (1 pascal = 1 newton per square metre, 1N/m). On average, a column of air with a cross-sectional area of 1 square centimetre (cm), measured from mean (average) sea level to the top of Earth's atmosphere,
3351423
Pressure sensor


may be used to describe a sensor that measures pressures below atmospheric pressure, showing the difference between that low pressure and atmospheric pressure, but it may also be used to describe a sensor that measures absolute pressure relative to a vacuum. This sensor measures the difference between two pressures, one connected to each side of the sensor. Differential pressure sensors are used to measure many properties, such as pressure drops across oil filters or air filters, fluid levels (by comparing the pressure above and below the liquid) or flow rates (
4708453
Bar (unit)


was used for a unit of weight in an early version of the metric system. Atmospheric air pressure is often given in millibars, where standard atmospheric pressure at sea level is defined as 1013.25 mbar, 101.325 kPa, 1.01325 bar, which is about . Despite the millibar not being an SI unit, meteorologists and weather reporters worldwide have long measured air pressure in millibars as the values are convenient. After the advent of SI units, some meteorologists began using hectopascals (symbol hPa) which are numerically equivalent to millibars; for the
5309134
Manifold vacuum


exposed to full atmospheric pressure, and maximum airflow through the engine is achieved. In a naturally aspirated engine, output power is limited by the ambient barometric pressure. Superchargers and turbochargers boost manifold pressure above atmospheric pressure. Modern engines use a manifold absolute pressure (abbreviated as "MAP") sensor to measure air pressure in the intake manifold. Manifold absolute pressure is one of a multitude of parameters used by the engine control unit (ECU) to optimize engine operation. It is important to differentiate between absolute and gauge pressure when
9206961
Pascal (unit)


the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa. The units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals (hPa) unit, equal to 100 pascals or 1 millibar. Exceptions include Canada, which use kilopascals (kPa). In many other fields of science, the SI is preferred
18012790
Pressure measurement


references, the following terms are used: The zero reference in use is usually implied by context, and these words are added only when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. For most working fluids where a fluid exists in a closed system, gauge pressure measurement prevails. Pressure instruments connected to the system will indicate pressures relative to the current atmospheric pressure. The situation changes when extreme vacuum pressures are measured,
20483547
Blowoff valve


manifold pressure drops below atmospheric pressure and the resulting pressure differential operates the blowoff valve's piston. The excess pressure from the turbocharger is then vented into the atmosphere or recirculated into the intake upstream of the compressor inlet. In the case where a mass airflow sensor (MAF) is used and is located upstream from the blowoff valve, the engine control unit (ECU) will inject excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements. The engine then briefly operates with a fuel-rich mixture after
20166
Pressure measurement


bar. The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64 lb/ft. According to the US Navy Diving Manual, one fsw equals 0.30643 msw, , or , though elsewhere it states that 33 fsw is (one atmosphere), which gives one fsw equal to about 0.445 psi. The msw and fsw are the conventional units for measurement of diver pressure exposure used in decompression tables and the unit of calibration for pneumofathometers and hyperbaric
20483558
Pressure measurement


device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: −15 psig or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure
20483545
Pressure


pressures are given in kilopascals (kPa) in most other fields, where the hecto- prefix is rarely used. The inch of mercury is still used in the United States. Oceanographers usually measure underwater pressure in decibars (dbar) because pressure in the ocean increases by approximately one decibar per metre depth. The standard atmosphere (atm) is an established constant. It is approximately equal to typical air pressure at Earth mean sea level and is defined as . Because pressure is commonly measured by its ability to displace a column of liquid
4049888
Useful conversions and formulas for air dispersion modeling


°F and 1 atmosphere. That being understood: 1 Nm³ of any gas (measured at 0 °C and 1 atmosphere of absolute pressure) equals 37.326 scf of that gas (measured at 60 °F and 1 atmosphere of absolute pressure). 1 kmol of any ideal gas equals 22.414 Nm³ of that gas at 0 °C and 1 atmosphere of absolute pressure ... and 1 lbmol of any ideal gas equals 379.482 scf of that gas at 60 °F and 1 atmosphere of absolute pressure. Notes: Meteorological data includes
9086657
Absolute scale


(e.g.: 15 psi of air in a tank at sea level will become 30 psi in the vacuum of space.) Therefore, with measurements of things like blood pressure or tire pressure, a measurement relative to air pressure is a better indication of "burst pressure" (damage threshold) than an absolute scale. Absolute scales are typically used in science, deep vacuum measurements (where the fluctuating pressure of the atmosphere becomes a nuisance), aeronautics (where precise measurements of the atmosphere are needed to determine altitude),
3569489
Admittance (geophysics)


In geophysics, admittance describes the small effects of atmospheric pressure on earth gravity. Studies have also been carried out regarding the gravity of Venus. Admittance in geophysics takes atmospheric pressure as the input and measures small changes in the gravitational field as the output. Geophysics admittance is commonly measured in μGal/mbar. These units convert according to 1 Gal = 0.01 m/s and 1 bar = 100 kPa, so in SI units the measurement would be in units of; formula_1   or   formula_2   or   formula_3   or, in primary units   formula_4
18810875
Pressure measurement


the difference in pressure between its two faces. The reference face can be open to atmosphere to measure gauge pressure, open to a second port to measure differential pressure, or can be sealed against a vacuum or other fixed reference pressure to measure absolute pressure. The deformation can be measured using mechanical, optical or capacitive techniques. Ceramic and metallic diaphragms are used. For absolute measurements, welded pressure capsules with diaphragms on either side are often used. shape: In gauges intended to sense small pressures or pressure differences, or require
20483584
Variometer


bottle) to augment the storage capacity of a common aircraft rate-of-climb instrument. In its simplest electronic form, the instrument consists of an air bottle connected to the external atmosphere through a sensitive air flow meter. As the aircraft changes altitude, the atmospheric pressure outside the aircraft changes and air flows into or out of the air bottle to equalise the pressure inside the bottle and outside the aircraft. The rate and direction of flowing air is measured by the cooling of one of two self-heating thermistors and the
20236394
Absolute scale


For this reason, the pressure relative to atmospheric pressure is called gauge pressure and measurements given in units like pounds per square inch (abbreviated lbf/in or psi) are often shown as "psig" (the "g" standing for gauge) or "psia" ("a" for absolute). Absolute scales are used when precise values are needed in comparison to a natural, unchanging zero point. Measurements of length, area and volume are inherently absolute, although measurements of distance are often based on an arbitrary
3569491
Atmospheric pressure


the local weather reports, they measure pressure adjusted to sea level, not the actual local atmospheric pressure. The "altimeter setting" in aviation is an atmospheric pressure adjustment. Average "sea-level pressure" is . In aviation, weather reports (METAR), QNH is transmitted around the world in millibars or hectopascals (1 hectopascal = 1 millibar), except in the United States, Canada, and Colombia where it is reported in inches of mercury (to two decimal places). The United States and Canada also
3351426
Calibration


of the Metric system. One of the earliest pressure measurement devices was the Mercury barometer, credited to Torricelli (1643), which read atmospheric pressure using Mercury. Soon after, water-filled manometers were designed. All these would have linear calibrations using gravimetric principles, where the difference in levels was proportional to pressure. The normal units of measure would be the convenient inches of mercury or water. In the direct reading hydrostatic manometer design on the right, applied pressure P pushes the liquid down the right side of the manometer
3351675
Pascal (unit)


is the newton, m is the metre, kg is the kilogram, s is the second, and J is the joule. One pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called an atmosphere or a standard atmosphere (atm) is . This value is often used as a reference pressure and specified as such in some national and international standards, such as the International Organization for Standardization's ISO 2787 (pneumatic tools and compressors),
18012786
Supermarine Spitfire variants: specifications, performance and armament


influences and can be used to indicate and measure "vacuum", or pressure below atmospheric pressure, as well. Mercury-filled manometers (devices capable of measuring pressures above and below atmospheric pressure also known as vacuum/boost gauges) that apply pressure directly to a column of liquid have much greater vacuum range when the fluid is much more dense than water. Subjecting water to pressures above or below atmospheric pressure raise or lowers its triple points and causes it to boil at "standard" temperature if subjected to more than one
19365508
Barometer


current measurement so a change can be seen. This type of barometer is common in homes and in recreational boats. It is also used in meteorology, mostly in barographs and as a pressure instrument in radiosondes. A barograph is a recording aneroid barometer where the changes in atmospheric pressure are recorded on a paper chart. Principle & Working: The principle of the barograph is same as that of the aneroid baromoter. A metal box partially exhausted of air will undergo changes of shape as the outside pressure varies. These small movements of
3351500
Inch of mercury


inches of mercury was the unit used to measure turbocharger inlet pressure. However, the inch of mercury is still used today in car performance modification to measure the amount of vacuum within the engine's intake manifold. This can be seen on boost/vacuum gauges. In air conditioning and refrigeration, inHg is often used to describe "inches of mercury vacuum", or pressures below ambient atmospheric pressure, for recovery of refrigerants from air conditioning and refrigeration systems, as well as for leak testing of systems while under a vacuum,
5622223
Heat capacity


and pressure" will both increase, even if the atmospheric pressure outside the container is kept constant. Therefore, the effective heat capacity of the gas, in that situation, will have a value intermediate between its isobaric and isochoric capacities formula_8 and formula_9. For complex thermodynamic systems with several interacting parts and state variables, or for measurement conditions that are neither constant pressure nor constant volume, or for situations where the temperature is significantly non-uniform, the simple definitions of heat capacity above are not useful or even meaningful. The
18647426
Pressure sensor


of pressure ranges they measure, temperature ranges of operation, and most importantly the type of pressure they measure. Pressure sensors are variously named according to their purpose, but the same technology may be used under different names. This sensor measures the pressure relative to perfect vacuum. This sensor measures the pressure relative to atmospheric pressure. A tire pressure gauge is an example of gauge pressure measurement; when it indicates zero, then the pressure it is measuring is the same as the ambient pressure. This term can cause confusion. It
4708452
Submarine depth ratings


Depth ratings are primary design parameters and measures of a submarine's ability to operate underwater. The depths to which submarines can dive are limited by the strengths of their hulls. Human occupants of a submarine would suffer physiological problems if the air pressure inside were simply allowed to be equal to the water pressure outside the hull (for example, oxygen becomes toxic at high pressures). So, when the inside air is kept at normal atmospheric pressure, the hull must be able to withstand the forces created by the outside water pressure
12692260
Dobson ozone spectrophotometer


. The results are measured in Dobson Units, equal to 10 µm thickness of ozone compressed to Standard conditions for temperature and pressure (STP) in the column. If all of the ozone in the atmospheric column one was measuring were compressed to STP, the thickness of the compressed atmosphere in mm would equal an answer in Dobson Units divided by 100. The vertical distribution of ozone is derived using the Umkehr method. This method relies on the intensities of reflected, rather than direct, UV light. Ozone distribution is derived from
1697483
Turgor pressure


. For example, a diatom doesn't have the same properties as a plant, which would place constrictions on what could be used to infer turgor pressure. Units used to measure turgor pressure are independent from the measures used to infer its values. Common units include bars, MPa, or newtons per square meter. 1 bar is equal to .1 MPa. Turgor pressure can be deduced when total water potential, Ψ, and osmotic potential, Ψ, are known in a water potential equation. These equations are used to measure
11452726
Sound pressure


Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa). A sound wave in a transmission medium causes a deviation (sound pressure, a "dynamic" pressure) in the local ambient pressure, a "static" pressure.br Sound pressure, denoted "p", is defined
18199654
Roentgen (unit)


this unit is used. The continued use of the roentgen is strongly discouraged by the NIST. Whilst a convenient quantity to measure with an air ion chamber, the rontgen had the disadvantage that it was not a direct measure of either the intensity of X-rays or their absorption, but rather was a measurement of the ionising effect of X-rays in a specific circumstance; which was dry air at 0 °C and 1 standard atmosphere of pressure. Because of this the roentgen had a variable relationship to the amount of
21645654
Cold inflation pressure


Excessive pressure, on the other hand, may lead to impact-breaks, decrease braking performance, and cause uneven wear (i.e., greater wear on the center part of the tire surface). Tire pressure is commonly measured in psi in the imperial and US customary systems, bar, which is deprecated but accepted for use with SI or the kilopascal (kPa), which is an SI unit. Ambient temperature affects the cold tire pressure. Absolute cold tire pressure (gauge pressure plus atmospheric pressure) varies directly with the
10456829
Vacuum


do not have universally agreed definitions, but a typical distribution is shown in the following table. As we travel into orbit, outer space and ultimately intergalactic space, the pressure varies by several orders of magnitude. Vacuum is measured in units of pressure, typically as a subtraction relative to ambient atmospheric pressure on Earth. But the amount of relative measurable vacuum varies with local conditions. On the surface of Jupiter, where ground level atmospheric pressure is much higher than on Earth, much higher relative vacuum readings would be possible. On
14117243
Vacuum


normally be considered a vacuum. Therefore, to properly understand the following discussions of vacuum measurement, it is important that the reader assumes the relative measurements are being done on Earth at sea level, at exactly 1 atmosphere of ambient atmospheric pressure. The SI unit of pressure is the pascal (symbol Pa), but vacuum is often measured in torrs, named for Torricelli, an early Italian physicist (1608–1647). A torr is equal to the displacement of a millimeter of mercury (mmHg) in a manometer with 1 torr
14117245
Mars suit


oxygen to avoid getting decompression sickness. A hard-suit can use a high-pressure atmosphere, eliminating the need to pre-breathe, but without being too hard to move like a high pressure soft suit would be. A simulated Mars suit was used for the HI-SEAS Earth-based spaceflight analog tests of the 2010s in Hawaii, USA. Mars suit design has been used as a topic for technology education. The Apollo lunar EVA suit was called the Extravehicular Mobility Unit (EMU). Besides the pressure suit
1604874
Atmospheric pressure


at which the vapor pressure is equal to the atmospheric pressure around the water. Because of this, the boiling point of water is lower at lower pressure and higher at higher pressure. Cooking at high elevations, therefore, requires adjustments to recipes or pressure cooking. A rough approximation of elevation can be obtained by measuring the temperature at which water boils; in the mid-19th century, this method was used by explorers. An important application of the knowledge that atmospheric pressure varies directly with altitude was in determining the height of hills and
3351437
Jewel Cave National Monument


System in Kentucky and Sistema Sac Actun at the Yucatán Peninsula (Mexico), at . The discovered areas in the cave account for only about 3 to 5% of the estimated total air volume of the cave. The cave volume is estimated by measuring the amount of air that the cave "exhales" when the outside air pressure drops and "inhales" when the outside air pressure rises. Jewel Cave is a "breathing cave," which means air enters or exits the cave with changes in atmospheric pressure from day to
1851885
Pressure head


converted into an absolute pressure using the above equations. If we had a column of mercury 767 mm high, we could calculate the atmospheric pressure as (767 mm)•(133 kN/m³) = 102 kPa. See the torr, millimeter of mercury, and pascal (unit) articles for barometric pressure measurements at standard conditions. The venturi meter and manometer is a common type of flow meter which can be used in many fluid applications to convert differential pressure heads into volumetric flow rate, linear fluid speed, or mass flow rate using
17248422
Geostrophic wind


nearly always balanced.) The geostrophic balance helps to explain why, in the northern hemisphere, low-pressure systems (or "cyclones") spin counterclockwise and high-pressure systems (or "anticyclones") spin clockwise, and the opposite in the southern hemisphere. Flow of ocean water is also largely geostrophic. Just as multiple weather balloons that measure pressure as a function of height in the atmosphere are used to map the atmospheric pressure field and infer the geostrophic wind, measurements of density as a function of depth in
1923834
Standard gravity


. In particular, it gives the conversion factor between newton and kilogram-force, two units of force. Already in the early days of its existence, the International Committee for Weights and Measures (CIPM) proceeded to define a standard thermometric scale, using the boiling point of water. Since the boiling point varies with the atmospheric pressure, the CIPM needed to define a standard atmospheric pressure. The definition they chose was based on the weight of a column of mercury of 760 mm. But since that weight depends on the
2418902
Cetane Improver


be ignited, Diesel fuel requires only the combination of the right pressure and temperature to start the combustion, with no outside assistance. The Cetane Number is a key property of Diesel fuel, as it measures its aptitude to self-ignite in the combustion chamber. The auto ignition temperature of Diesel fuel is around 220 °C at atmospheric pressure. Cetane Improver additives are used to decrease this temperature and lead to quicker combustion, by increasing the Cetane number. By reducing ignition time, Cetane Improver additives affect engine emissions, and
5754024
National Institute of Water and Atmospheric Research


future atmospheric changes have also been developed at Lauder, and the atmospheric measurements taken at Lauder are used in climate models around the world. Measurements of the atmosphere at Lauder can be carried out in situ, and through remote sensing. In situ measurements are mostly done at ground-level; however balloons are launched weekly and carry out in situ measurements through the atmosphere to altitudes of approximately 30 km. Data from these balloons enables atmospheric profiles of temperature, pressure, water vapour, and ozone to be produced. One method of
7536020
Absolute scale


Reaumur) or the lowest temperature attainable in 1724 (Fahrenheit). Pressure is a force that can be measured absolutely, because the natural minimum of pressure is total vacuum. Pressure is frequently measured with reference to atmospheric pressure rather than on any absolute scale, relative to complete and perfect vacuum; it is technologically simpler and cheaper. It may also be more convenient to use relative scales, because, with things like pneumatics and hydraulics, the amount of energy transferred is reduced by the relative "backpressure" of the atmosphere.
3569488
Diving cylinder


decimal place accuracy. These are representative examples, for a larger range, the on-line catalogues of the manufacturers such as Faber, Pressed Steel, Luxfer, and Catalina may be consulted. The applications are typical, but not exclusive. The nominal volume of gas stored is commonly quoted as the cylinder capacity in the USA. It is a measure of the volume of gas that can be released from the full cylinder at atmospheric pressure. Terms used for the capacity include 'free gas volume' or 'free gas equivalent
9657376
Metre sea water


when a pressure difference is measured between the locks of a hyperbaric chamber, which is also generally measured in fsw and msw. The pressure of seawater at a depth of 33 feet equals one atmosphere. The absolute pressure at 33 feet depth in sea water is a combination of atmospheric and hydrostatic pressure for that depth, and is 66 fsw, or two atmospheres absolute. For every additional 33 feet of depth, another atmosphere of pressure accumulates. Therefore at the surface the gauge pressure of 0 fsw is equivalent to an absolute pressure
5213489
Vacuum


equaling 133.3223684 pascals above absolute zero pressure. Vacuum is often also measured on the barometric scale or as a percentage of atmospheric pressure in bars or atmospheres. Low vacuum is often measured in millimeters of mercury (mmHg) or pascals (Pa) below standard atmospheric pressure. "Below atmospheric" means that the absolute pressure is equal to the current atmospheric pressure. In other words, most low vacuum gauges that read, for example 50.79 Torr. Many inexpensive low vacuum gauges have a margin of error and may report a vacuum of
14117246
Pounds per square inch


than ambient atmospheric pressure, then the units would be pounds per square inch differential (psid). The kilopound per square inch (ksi) is a scaled unit derived from psi, equivalent to a thousand psi (1000 lbf/in). ksi are not widely used for gas pressures. They are mostly used in materials science, where the tensile strength of a material is measured as a large number of psi. The conversion in SI units is 1 ksi = 6.895 MPa, or 1 MPa = 0.145 ksi. The
11239321
Volume and extent of the Deepwater Horizon oil spill


by the Flow Rate Technical Group—scientists from the National Oceanic Atmospheric Administration (NOAA), United States Geological Survey (USGS), Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE), U.S. Department of Energy (DOE), and outside academics, led by USGS director Marcia McNutt. The later estimates were believed to be more accurate because it was no longer necessary to measure multiple leaks, and because detailed pressure measurements and high-resolution video had become available. According to BP, estimating the oil flow
6432141
Great Blizzard of 1978


out at . Toronto pressure fell to 28.40 inches, breaking its old record by 0.17. The barometric pressure measurement recorded in Mount Clemens, Michigan was the third lowest non-tropical atmospheric pressure recorded in the mainland United States and the lowest in the Central United States. The lowest confirmed pressure for a non-tropical system in the continental United States had been set by a January 1913 Atlantic coast storm. The lowest central pressure for the 1978 blizzard was measured in Sarnia, Ontario, Canada. On rare occasions, extra-
17004611
Hurricane Ava


It was the first Pacific hurricane penetrated by National Oceanographic and Atmospheric Administration aircraft, but not by aircraft from other agencies. NOAA craft were laden with sensors and measured wave heights reaching with a microwave radar system and a laser altimeter. That was the first time ever that sea conditions in a tropical cyclone had been measured that way. United States Air Force planes measured central pressure, air temperature, and humidity in the eye pressures using dropsondes. The collection of data from both space and the air was done in order to allow
5533554
Thermodynamic instruments


state of the system being controlled. The term "atmospheric pressure" in the below description of a theoretical thermometer is essentially a "pressure reservoir" which imposes atmospheric pressure upon the thermometer. Some common reservoirs are: Let's assume that we understand mechanics well enough to understand and measure volume, area, mass, and force. These may be combined to understand the concept of pressure, which is force per unit area and density, which is mass per unit volume. It has been experimentally determined that, at low enough
12082333
Atmospheric pressure


Ocean. The measurement was based on an instrumental observation made from a reconnaissance aircraft. One atmosphere (101.325 kPa or 14.7 psi) is also the pressure caused by the weight of a column of fresh water of approximately 10.3 m (33.8 ft). Thus, a diver 10.3 m underwater experiences a pressure of about 2 atmospheres (1 atm of air plus 1 atm of water). Conversely, 10.3 m is the maximum height to which water can be raised using suction under standard atmospheric conditions. Low pressures such as natural
3351435
DP cell


A DP cell is a device that measures the differential pressure between two inputs. Example: To measure the pressure difference between a container (or vessel) and the surrounding atmosphere, you may connect 'Hi' port of the DP-cell to a fitting that enters the vessel, using suitable tubing. The 'Lo' port, you leave open to the atmosphere (open air, or possibly through a buffer or desiccant chamber). The DP-cell will indicate the relative difference between the pressure of the vessel (
21121007
Ultra-high vacuum


Hydrogen and carbon monoxide are the most common background gases in a well-designed, well-baked UHV system. Both Hydrogen and CO diffuse out from the grain boundaries in stainless steel. Helium could diffuse through the steel and glass from the outside air, but this effect is usually negligible due to the low abundance of He in the atmosphere. Measurement of high vacuum is done using a "nonabsolute gauge" that measures a pressure-related property of the vacuum, for example, its thermal conductivity. See, for example
6574158
Barometer


A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, 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 used at different levels matching the corresponding atmospheric pressure to the altitude, while a barometer
3351476
Positive pressure enclosure


be checked & downloaded on the IECEx certification website. IECEx certification is compulsory to operate electrical equipment in explosive atmosphere in most Countries outside Europe. Australia, New Zealand, UAE, Malaysia, and the Philippines accept IECEx certification directly. In Canada and the USA, all electrical equipment must bear the recognized Certification Mark of an accredited Certification Body, i.e., cQPS for Canada, QPSus for the USA and cQPSus for both, the USA and Canada. This QPS mark is only an extension of the IECEx certification - meaning IECEx +
18716414
Pascal (unit)


The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa) which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa) which is equal to one centibar. The unit of measurement called standard atmosphere (atm)
18012784
Gas blending for scuba diving


a pressure drop, as they directly measure partial pressure, and this may lead to a mix richer than intended, as the oxygen flow may be set to the partial pressure appropriate for atmospheric pressure, while the measured mixture is at a lower pressure. This can be compensated by using a small sampling pump drawing gas from the blending tube and delivering it to the instruments, or by allowing for the reduced inlet pressure for oxygen analysis with an in-line sensor cell. This would require a vacuum gauge measuring the pressure drop
13557488
Voyager 1


on sunlight and Earth-based measurement of its effect on the probe's radio signal were used to determine the atmosphere's composition, density, and pressure. Titan's mass was also measured by observing its effect on the probe's trajectory. The thick haze prevented any visual observation of the surface, but the measurement of the atmosphere's composition, temperature, and pressure led to speculation that lakes of liquid hydrocarbons could exist on the surface. Because observations of Titan were considered vital, the trajectory chosen for "Voyager 1"
14364558
Acoustic ohm


The acoustic ohm is a unit of measurement of acoustic impedance, which is the ratio of acoustic pressure to acoustic volume flow. In SI units, pressure is measured in pascals and flow in m/s, so the acoustic ohm has units Pa•s/m. In the cgs system, there is a cgs ohm with units dyne•s/cm. The acoustic ohm can be applied to fluid flow outside the domain of acoustics. For such applications a hydraulic ohm with an identical definition may be used. That is, the unit
9492264
Altimeter


An altimeter or an altitude meter is an instrument used to measure the altitude of an object above a fixed level. The measurement of altitude is called altimetry, which is related to the term bathymetry, the measurement of depth under water. Altitude can be determined based on the measurement of atmospheric pressure. The greater the altitude, the lower the pressure. When a barometer is supplied with a nonlinear calibration so as to indicate altitude, the instrument is called a pressure altimeter or barometric altimeter. A pressure altimeter is the altimeter found
3351320
Atmosphere of Earth


megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather. If the entire mass of the atmosphere had a uniform density equal to sea level density (about 1.2 kg per m) from sea level upwards, it would terminate abruptly at an altitude of . It actually decreases exponentially with altitude, dropping by half every or by a factor of 1/e every ,
21257677
Pressure measurement


vacuum if its vapor pressure is too high. When measuring liquid pressure, a loop filled with gas or a light fluid can isolate the liquids to prevent them from mixing, but this can be unnecessary, for example, when mercury is used as the manometer fluid to measure differential pressure of a fluid such as water. Simple hydrostatic gauges can measure pressures ranging from a few torrs (a few 100 Pa) to a few atmospheres (approximately ). A single-limb liquid-column manometer has a larger reservoir instead of
20483571
Airspace class (United States)


the contiguous United States and Alaska. Unlike the altitude measurements used in other airspace classes, the FLnnn flight levels used in class A airspace are pressure altitudes referenced to a standardized altimeter setting of 29.92" Hg and thus the true altitudes depend on local atmospheric pressure variations. Unless otherwise authorized by ATC, all flight operations in class A airspace must be under ATC control, and must be operating IFR, under a clearance received prior to entry. An example of an exception to IFR-only flight in this airspace is the use
19707314
Meteorological instrumentation


the first hair hygrometer is demonstrated by Horace-Bénédict de Saussure. In 1806, Francis Beaufort introduced his system for classifying wind speeds. The April 1960 launch of the first successful weather satellite, TIROS-1, marked the beginning of the age where weather information became available globally. This was also used to measure the temperature of the surrounding air. A thermometer measures air temperature, or the kinetic energy of the molecules within air. A barometer measures atmospheric pressure, or the pressure exerted by the weight of the Earth's atmosphere above
19972708
Kymograph


of physiological phenomena such as breathing, muscle movement, speech. New detection and registration systems included electrical and electronic methods, and plotted in ink. Kymographs were also used outside medical science to measure atmospheric pressure, tuning fork vibrations, the functioning of steam engines, animal habits and the movement of molecules in cells. Kymograph is generally used to study the effects of xenobiotics on tissue preparations. It is a standalone recording apparatus used alongside other apparatus such as organ bath. Writing levers are used to trace the recording from muscle contractions
16698576
Partial pressure


is the pressure of a vapor in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid's tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquid's atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point. The higher the vapor pressure of a liquid at a
74023
Work (thermodynamics)


changes. "PV" work is often measured in units of litre-atmospheres where = . However, the litre-atmosphere is not a recognised unit in the SI system of units, which measures P in Pascal (Pa), V in m, and PV in Joule (J), where 1 J = 1 Pa·m. "PV" work is an important topic in chemical thermodynamics. For a process in a closed system, occurring slowly enough for accurate definition of the pressure on the inside of the system's
11409923
Multiphase flow meter


meter measures the flow rates at line pressures, which are typically orders of magnitude greater than atmospheric pressure, but the meter must report the oil and gas volumes at standard (atmospheric) pressure and temperature. The meter must thus know the Pressure / Volume / Temperature properties of the oil, to add to the measured gas rate at line pressure the additional gas that would be liberated from the oil at atmospheric pressure, and also know the loss in oil volume from the release of that gas in conversion to standard conditions. With
17219725
Atmosphere (unit)


The standard atmosphere (symbol: atm) is a unit of pressure defined as . It is sometimes used as a "reference" or "standard pressure". It is approximately equal to the atmospheric pressure at sea level. It was originally defined as the pressure exerted by 760 mm of mercury at 0 °C and standard gravity ("g" = ). It was used as a reference condition for physical and chemical properties, and was implicit in the definition of the Centigrade (later Celsius) scale of temperature by
14593127
GRACE and GRACE-FO


thinning of ice sheets to the flow of water through aquifers and the slow currents of magma inside Earth, mass measurements provided by GRACE help scientists better understand these important natural processes. GRACE chiefly detected changes in the distribution of water across the planet. Scientists use GRACE data to estimate ocean bottom pressure (the combined weight of the ocean waters and atmosphere), which is as important to oceanographers as atmospheric pressure is to meteorologists. For example, measuring ocean pressure gradients allows scientists to estimate monthly changes in deep ocean currents. The
7486818
NACA Report No. 107


them have proved satisfactory for use under conditions of actual practice from 200 to 2,600 rpm (the highest engine speed available for test), and from 10 pounds/in² below atmospheric pressure to 1,000 psi above. The instrument has proved convenient in use and of high accuracy, being capabIe of measuring pressures to an accuracy comparable with that of the standard 6-inch pressure gauges used for recording these pressures. It is suited to measuring the pressures in internal combustion engines, as well as in any engine, compressor, or other machine in
3216110
Flight level


In aviation and aviation meteorology, flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa (29.92 inHg), and therefore is not necessarily the same as the aircraft's actual altitude either above sea level or above ground level. Flight levels are used to ensure safe vertical separation between aircraft, despite natural local variations in atmospheric air pressure. Historically, altitude has been measured using a pressure altimeter,
12955624
Calibration


U-tube, while a length scale next to the tube measures the difference of levels. The resulting height difference "H" is a direct measurement of the pressure or vacuum with respect to atmospheric pressure. In the absence of differential pressure both levels would be equal, and this would be used as the zero point. The Industrial Revolution saw the adoption of "indirect" pressure measuring devices, which were more practical than the manometer. An example is in high pressure (up to 50 psi) steam engines, where
3351676
Ambient pressure


such as meteorology and underwater diving, it is common to see ambient pressure expressed in bar or millibar. One bar is 100 kPa or approximately ambient pressure at sea level. Ambient pressure may in other circumstances be measured in pounds per square inch (psi) or in standard atmospheres (atm). The ambient pressure at sea level is approximately one atmosphere, which is equal to , which is close enough for bar and atm to be used interchangeably in many applications. Pressures are given in terms of the normal ambient pressure experienced
15451530
Pressure measurement


Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges or vacuum gauges. A manometer is a good example, as it uses a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical
20483544
GPS meteorology


the measured air pressure at the surface, and obtain a measure for the absolute water vapour content of the atmosphere, integrated from surface to space. This is also referred to as "total precipitable water vapour". What makes it possible to determine the total atmospheric delay, is its known dependence of the zenith or elevation angle of the satellite. If formula_1 is the zenith angle, the propagation path delay is proportional to formula_2. This unique signature makes it possible to solve separately for the "zenith delay" in GPS computations
14391986
Atmosphere of Earth


1.2 kg/m (1.2 g/L, 0.0012 g/cm). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used to predict orbital decay of satellites. The average mass of the atmosphere is about 5 quadrillion (5) tonnes or 1/1,200,000 the mass of Earth
21257682
Pressure sensor


by measuring the change in pressure across a restriction). Technically speaking, most pressure sensors are really differential pressure sensors; for example a gauge pressure sensor is merely a differential pressure sensor in which one side is open to the ambient atmosphere. This sensor is similar to a gauge pressure sensor except that it measures pressure relative to some fixed pressure rather than the ambient atmospheric pressure (which varies according to the location and the weather). There are two basic categories of analog pressure sensors, Force collector types These types of electronic
4708454
Litre


point of maximum density (3.984 °C) under one standard atmosphere (760 Torr, 101.325 kPa) of pressure. The litre, though not an official SI unit, may be used with SI prefixes. The most commonly used derived unit is the millilitre, defined as one-thousandth of a litre, and also often referred to by the SI derived unit name "cubic centimetre". It is a commonly used measure, especially in medicine, cooking and automotive engineering. Other units may be found in the table below
18304388
Pressure measurement


cable or a hole on the side of the device, so that it always measures the pressure referred to ambient barometric pressure. Thus a vented-gauge reference pressure sensor should always read zero pressure when the process pressure connection is held open to the air. A sealed gauge reference is very similar, except that atmospheric pressure is sealed on the negative side of the diaphragm. This is usually adopted on high pressure ranges, such as hydraulics, where atmospheric pressure changes will have a negligible effect on the accuracy of the reading,
20483551
Pressure


; similarly, the pound-force per square inch (psi) is the traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmospheric pressure; the atmosphere (atm) is equal to this pressure, and the torr is defined as of this. Manometric units such as the centimetre of water, millimetre of mercury, and inch of mercury are used to express pressures in terms of the height of column of a particular fluid in a manometer. Pressure is the amount
4049881
List of atmospheric pressure records in Europe


914.0mb affected the UK during the Braer Storm on 10 January 1993, however this figure is discounted as this reading was not recorded in the UK. In the period of instrumental measurement the atmospheric pressure has exceeded 1048 hPa somewhere over the United Kingdom and Ireland on 17 occasions. On nine of these times, the pressure exceeded 1050 hPa—a value not exceeded since 1957 in Ireland, and since 26 January 1932 over the UK. Intense high pressure is usually seen during midwinter with 7 of the 9 occasions where 1050 hPa
9084646
Standard conditions for temperature and pressure


in their various standards and regulations. Notes: In aeronautics and fluid dynamics the "International Standard Atmosphere" (ISA) is a specification of pressure, temperature, density, and speed of sound at each altitude. The International Standard Atmosphere is representative of atmospheric conditions at mid latitudes. In the USA this information is specified the U.S. Standard Atmosphere which is identical to the "International Standard Atmosphere" at all altitudes up to 65,000 feet above sea level. Due to the fact that many definitions of standard temperature and pressure differ in
8173632
Pressure measurement


negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 30 inHg (typical atmospheric pressure) − 26 inHg = 4 inHg. Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the (gauge) tire pressure goes up because atmospheric pressure goes down. The
20483549
Pressure measurement


so venting is not necessary. This also allows some manufacturers to provide secondary pressure containment as an extra precaution for pressure equipment safety if the burst pressure of the primary pressure sensing diaphragm is exceeded. There is another way of creating a sealed gauge reference, and this is to seal a high vacuum on the reverse side of the sensing diaphragm. Then the output signal is offset, so the pressure sensor reads close to zero when measuring atmospheric pressure. A sealed gauge reference pressure transducer will never read exactly zero because atmospheric pressure is
20483552
History of the petroleum industry in Canada (oil sands and heavy oil)


6.29 barrels. One cubic metre of natural gas = 35.49 cubic feet. One kilopascal = 1% of atmospheric pressure (near sea level). Canada's oil measure, the cubic metre, is unique in the world. It is metric in the sense that it uses metres, but it is based on volume so that Canadian units can be easily converted into barrels. In the rest of the metric world, the standard for measuring oil is the metric tonne. The advantage of the latter measure is that it reflects oil
13131750
Motorcycle testing and measurement


can be accurately quantified & corrected for. Explicit guidance on the homologation measurements and transmission corrections is given in directive 95/1/EC. A main source of ambiguity and differences comes from the conditions the test was done at. These conditions include details like atmospheric conditions (temperature, pressure, humidity), tire pressure, but most importantly: the conditions of the motorcycle itself. Examples thereof are: was the alternator fitted?; was the air filter fitted?; what exhaust system was fitted? One would hope that manufacturers would
13077329
Mars Climate Orbiter


and $42.8 million for mission operations. The Pressure Modulated Infrared Radiometer (PMIRR) uses narrow-band radiometric channels and two pressure modulation cells to measure atmospheric and surface emissions in the thermal infrared and a visible channel to measure dust particles and condensates in the atmosphere and on the surface at varying longitudes and seasons. Its principal investigator was Daniel McCleese at JPL/CALTECH. Similar objectives were later achieved with "Mars Climate Sounder" on board "Mars Reconnaissance Orbiter". Its objectives: The Mars Color Imager (MARCI)
12743774
Pressure


pressure", but relative to atmospheric pressure; such measurements are called "gauge pressure". An example of this is the air pressure in an automobile tire, which might be said to be "", but is actually 220 kPa (32 psi) above atmospheric pressure. Since atmospheric pressure at sea level is about 100 kPa (14.7 psi), the absolute pressure in the tire is therefore about . In technical work, this is written "a gauge pressure of ". Where space is limited, such as on
4049896
Number density


" does not depend much on the size or shape of the volume "V". In SI units, number density is measured in m, although cm is often used. However, these units are not quite practical when dealing with atoms or molecules of gases, liquids or solids at room temperature and atmospheric pressure, because the resulting numbers are extremely large (on the order of 10). Using the number density of an ideal gas at and as a yardstick: is often introduced as a unit of number density,
9991378
Sphygmomanometer


A sphygmomanometer, also known as a blood pressure meter, blood pressure monitor, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or mechanical manometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. Manual sphygmomanometers are used in conjunction with a stethoscope. A sphygmomanometer
19593779
Duct leakage testing


measuring the amount of flow that is required to equalize the pressure. Another form of duct leakage to outside uses a blower door to measure the total amount of leakage of the house, then seal off all registers and returns and to measure the leakage again. The next step requires measuring the pressure in the taped off duct system with respect to the building. The blower door manual will include a correction table to determine a correction factor based on the pressure in the duct work. To calculate the duct leakage to outside, subtract
16356972
Mariotte's bottle


reservoir is supplied with an air inlet and a siphon. The pressure at the bottom of the air inlet is always the same as the pressure outside the reservoir, i.e. the atmospheric pressure. If it were greater, air would not enter. If the entrance to the siphon is at the same depth, then it will always supply the water at atmospheric pressure and will deliver a flow under constant head height, regardless of the changing water level within the reservoir. This apparatus has many variations in design and has been used extensively
2573140
Atmospheric sounding


Atmospheric sounding or atmospheric profiling is a measurement of vertical distribution of physical properties of the atmospheric column such as pressure, temperature, wind speed and wind direction (thus deriving wind shear), liquid water content, ozone concentration, pollution, and other properties. Such measurements are performed in a variety of ways including remote sensing and in situ observations. The most common in situ sounding is a radiosonde, which usually is a weather balloon, but can also be a rocketsonde. Remote sensing soundings generally use passive infrared and microwave radiometers
210842
Surface weather analysis


created and displayed over the next several years. The pressureNET project is an ongoing attempt to gather surface pressure data using smartphones. When analyzing a weather map, a station model is plotted at each point of observation. Within the station model, the temperature, dewpoint, wind speed and direction, atmospheric pressure, pressure tendency, and ongoing weather are plotted. The circle in the middle represents cloud cover; fraction it is filled in represents the degree of overcast. Outside the United States, temperature and dewpoint are plotted in degrees
21616160