Iso uom list

We would also like to keep this specification maintainable and flexible to update. Although the initial version contains more than terminal unit symbols more than three times as many symbols as in ANSI X3. The specification is maintained electronically so that the printed version is guaranteed to contain consistent and tested data that is free from severe name conflicts or random errors.

There is a set of functional tests for UCUM implementations. All comments are welcome and are usually responded to within only few business days. From now on we will also post all email exchanges with responses in order to maintain accountability for any changes and community input. See the CommentsArchive for these. Powered by Trac 1. Wiki Roadmap View Tickets. What is it? For example, the older CGM-units dyne and erg are still used in the science of physiology. For example it doesn't define the degree Fahrenheit.

The metric predicate accounts for the fact that there are units that are prefixed and others that are not. This helps to disambiguate the parsing of simple units into prefix and atom. To determine whether a given unit atom is metric or not is not trivial. It is a cultural phenomenon, subject to change, just like language, the meaning of words and how words can be used. At one time we can clearly tell right or wrong useage of words, but these decisions may need to be revised with the passage of time.

Metric units are usually based on reproducible natural phenomena and are usually not part of a system of compareable units with different magintudes, especially not if the ratios of these units are not powers of Instead, metric units use multiplier prefixes that magnify or diminish the value of the unit by powers of ten.

Conversely, customary units are in the spirit of the middle age as most of them can be traced back into a time around the 10th century, some are even older from the Roman and Babylonian empires. Most customary units are based on the average size of human anatomical or botanic structures e. Thus all customary units are non-metric. Not all units from ISO are metric as degree, minute and second of plane angle are non-metric as well as minute, hour, day, month, and year.

The second is a metric unit because it is a part of the SI basis, although it used to be part of a series of customary units originating in the Babylonian era. Furthermore, for a unit to be metric it must be a quantity on a ratio scale where multiplication and division with scalars are defined. This statement has not been made explicitly before. This is an unfortunate decision because difference-scale units like the degree Celsius have no multiplication operation, so that the prefix value could be multiplied with the unit.

Instead the prefix at non-ratio units scales the measurement value. New submissions of unit atoms, however, must conform to the style rules. For example when distinguishing the International Table calorie from the thermochemical calorie, we would use 1 cal IT or 1 cal th in print. Other examples are the distinctions between the Julian and Gregorian calendar year from the tropical year or the british imperial gallon from the U.

Customary units are defined in The Unified Code for Units of Measure in order to accomodate practical needs.

However metric units are still prefered and the customary symbols should not interfere with metric symbols in any way. If unit symbols for the purpose of display and print are derived from The Unified Code for Units of Measure units, the square brackets can be removed. But every semantic element may have more than one valid representant in The Unified Code for Units of Measure. All expressions that are equal are also commensurable but not all commensurable expressions are equal. The set D of dimensions is infinite in principle, but only a finite subset of dimensions are used in practice.

Thus, implementations of The Unified Code for Units of Measure need not be able to represent the infinite set of dimensions. Thus if memory is limited, 4 bit per component of the dimension vector could be sufficient.

Therefore those special semantic entities are called special units , as opposed to proper units. The functions f s and f s -1 are applied as follows: let r s be the numeric measurement value expressed in the special unit s and let m be the corresponding dimensioned quantity, i. Multiplication of a special unit s with a dimensionless unit r 1 is defined as r s. Since prefixes have a scalar value that multiplies the unit atom, a unit must at least have a defined multiplication operation with a scalar in order to be a candidate for the metric predicate.

All proper units are candidates for the metric property, special units are no such candidates. These units have no general meaning in relation with any other unit in the SI. Therefore those arbitrary semantic entities are called arbitrary units , as opposed to proper units.

Until version 1. Since version 1. Tera and giga have a second letter to be safe in the future. Full name and print symbol are defined by other bodies and are out of scope of The Unified Code for Units of Measure. Any other basis B ' that generates an isomorphic group of units is conformant with The Unified Code for Units of Measure. Special units can not be base units.

The replacement of the kilogram is trivial. In order to bring syntax and semantics in line we can not have a unit with prefix in the base. The base unit kilogram is one of the oddities of the SI: if the gram would have been chosen as a base units the CGPM could have saved the rather annoying exception of the prefixing rules with the kilogram.

At times where we have to multiply the wavelength of excited krypton atoms by The rationale for removing the mole from the base is that the mole is essentially a count of particles expressed in a unit of very high magnitude Avogadro's number. There is no fundamental difference between the count of particles and the count other things.

The definition is a valid case sensitive expression of The Unified Code for Units of Measure that defines the unit atom. The explicit powers of ten should be given instead. Without reference to history, it is difficult to explain that the degree Celsius is part of the SI, because the degree Celsius is in a unique way incoherent with the SI, and is even superfluous since the base unit kelvin measures the same kind of quantity.

ANSI X3. The semantics of the units of time is difficult to capture. The difficulties start with the day: There is the sidereal and the solar day that depend on the earth's rotation. The earth's rotation is variable during one day and is continually slowing down in the long run. The usual subdivisions of the day in 24 hours of 60 minutes and 60 seconds originated in Babylonia.

The earth's rotation was too inexact to measure time, which is why the 11th CGPM defined the second based on a standarized historical tropical year see below which was later 13th CGPM replaced by frequency measurement. Thus the second came to be the base unit of time and the day is now s exactly with the Universal Coordinated Time UTC adding leap seconds every now and then. And both are difficult. The tropical year is the year defined by time the earth travels around the sun.

This is difficult to measure and varies over time. Around it was In addition these durations are averages. The actual length of each year may vary by several minutes due to the gravitational influence of other planets. Thus there is quite a high uncertainty already in the fourth decimal digit. The calendar year is also difficult because there is the Julian calendar Sosigenes of Alexandria and Julius Caesar, 45 BC with a slightly too long year of The Gregorian mean year is thus This leap year arithmetic seems to be too much even for astronomers, which is why the light year ends up being defined based on the Julian year [NIST Sp.

For this reason The Unified Code for Units of Measure defines Tropical, Julian and Gregorian year by means of subscripts, but assigns the default year symbol to the Julian year. The week is 7 days, this is a biblic truth we can count on it is actually quite plausible that the week of seven days originated in Babylonia and entered Jewish tradition during the Babylonian exile.

The difficultiy continues with the month. The calendar month is difficult because of the uneven distribution of days in a month over the year, and because of the two different calendar years. But we will usually use the mean calendar month, which is the Julian calendar year divided by The SI has fixated the second which should be used whenever accuracy is required.

For business purposes the Julian calendar is sufficient especially since the notion of the Work-Day vs. Holiday is more important than the imprecision over years. Claus Tondering, Frequently asked questions about calendars. Part 1. This list is not complete. It does not list all constants but only those that are fundamental and from which many other constants can be derived.

CGS units are still used in many physiological laboratories and in clinical diagnostics e. In addition CGS units ackquired a special dignity as this was the system of units used by the great physicists of the early 20th century, Albert Einstein, Max Planck, and many others who worked on the scientific revolution that had quite a cultural impact. This table was compiled from various sources and is not complete and not very systematic. We therefore welcome suggestions and advice as to how this table could be completed.

Customary units have once been used all over Europe. Units were taken from nature: anatomical structures e. Many of these units can be traced back in history to the Romans mile , Greeks carat and even more ancient times.

It is thus no wonder that this heritage was in some way ordered. Indeed, one finds the same names for units used in different countries and most of these units where divided into smaller or multiplied to larger units in the same way. For example, there was the foot de. An inch was divided into 12 lines de. Ampere Tum Per Centimetre. A unit of length equal to one hundred-millionth of a centimetre, 10—10 metre, used mainly to express wavelengths and interatomic distances.

A unit of measure for blood potency. Anti-Hemophilic Factor Ahf Unit. A unit of count defining the number of assortments assortment: set of items grouped in a mixed collection. Astronomical Unit. Average Minute Per Call. Bar unit of pressure. Barn Per Electron Volt. Barn Per Steradian Electron Volt,. Barn Per Sterdian. Barrel Us Per Day. Barrel Per Minute. There are varying standards for barrel for some specific commodities, including 31 gal for beer, 40 gal for whiskey or kerosene, and 42 gal for petroleum.

Barrel, Imperial. A unit of area of sheets of tin mil products tin plate, tin free steel or black plate 14 by 20 inches, or 31, square inches. Beats Per Minute. The SI derived unit of radioactivity. Becquerel Per Kilogram. Becquerel Per Metre Cubed.

In telecommunications and computing, bitrate sometimes written bit rate, data rate or as a variable R or fb is the number of bits that are conveyed or processed per unit of time. A unit of count defining the number of books book: set of items bound together or written document of a material whole. Brake Horse Power. British thermal unit. A traditional unit of energy.

British Thermal Unit Per Hour. British Thermal Unit Per Pound. Btu Per Cubic Foot. A bushel is an imperial and U. It is used for volumes of dry commodities not liquids , most often in agriculture.

Calorie - Calorie Per Cubic Centimetre. Calorie Per Gram. Candela per Square Metre. A unit of count defining the number of units of card card: thick stiff paper or cardboard. Carrying Capacity In Metric Ton. A centimetre is equal to one hundredth of a metre. Centimetre Per Second. Centisimal Hahnemannian Dilution CH.

Colony Forming Units. Composite Product Pound Total Weight. Conference Point. Conventional Millimetre Of Mercury. Conventional millimetre of mercury mm Hg. Conventional Millimetre Of Water. Coulomb Metre Squared Per Volt. Coulomb Per Cubic Centimetre. Coulomb Per Cubic Metre. Coulomb Per Cubic Millimetre. Coulomb Per Kilogram. Coulomb Per Kilogram Second. Coulomb Per Mole. Coulomb Per Square Centimetre. Coulomb Per Square Metre.

Coulomb Per Square Millimetre. Count Per Centimetre. Count Per Minute. Cubic centimetre. A cubic centimetre is the volume of a cube of side length one centimetre 0. Cubic Centimetre Per Mole. Cubic Centimetre Per Second.

Cubic decimetre. A cubic decimetre is the volume of a cube of side length one decimetre 0. Cubic Decimetre Per Mole. A cubic foot is the volume of a cube of side length one foot 0. Cubic Foot Per Hour. Cubic Foot Per Minute. A cubic inch is the volume of a cube of side length one inch 0.

A cubic metre is the volume of a cube of side length one metre. Cubic Metre Net. Cubic Metre Per Coulomb. Cubic Metre Per Hour.

Cubic Metre Per Kilogram. Cubic Metre Per Mole. Cubic Metre Per Second. Cubic millimetre. A cubic millimetre is the volume of a cube of side length one milliimetre 0. Cup US. Curie Per Kilogram. Deadweight Tonnage. A unit of mass defining the difference between the weight of a ship when completely empty and its weight when completely loaded, expressed as the number of tons.

Decilitre Per Gram. A decimetre is equal to one tenth of a metre. Decinewton Metre. Degree Unit of Angel. Degree Fahrenheit. Displacement Tonnage. Dollar Per Hour. A unit of count defining the number of doses dose: a definite quantity of a medicine or drug. A unit of count defining the number of dots per linear inch as a measure of the resolution or sharpness of a graphic image. A unit of count defining the number of units in multiples of The dram archaic spelling drachm was historically both a coin and a weight.

Dry Barrel Us. Dry Gallon Us. Dyn Second Per Cubic Centimetre. Dyne Per Centimetre. Dyne Per Square Centimeter. Dyne Second Per Centimetre. A unit of count defining the number of items regarded as separate units.

Electronic Mail Box. Electronvolt Per Metre. Electronvolt Square Metre. Electronvolt Square Metre Per Kilogram. Enzyme-linked immunosorbent assay unit, is always associated with a product and a method. Equivalent Gallon. Erg Per Centimetre. Erg Per Cubic Centimetre.

Erg Per Gram Second. Erg Per Second Square Centimetre. Erg Per Square Centimetre Second. Erg Square Centimetre. Erg Square Centimetre Per Gram. Failure Rate In Time. Farad Per Metre. Fifteen Kg Drum. Fifty Lb Bulk Bag. Fiftyfive Gallon Us Drum. Fivehundred Kg Bulk Bag. Fluid ounce UK. Fluid ounce US. The international foot is defined to be equal to 0. Foot Per Minute. Foot Per Second. Foot Per Second Squared. Foot Pound-Force. Foot Pound-Force Per Second. Forty Foot Container.

Fuel Usage Gallon Us. The imperial UK gallon was legally defined as 4. The U. Gallon Us Per Day. Gallon Per Thousand Cubic Feet. Gallon Us Per Thousand. A number referring to the outer diameter of hypodermic or suture needles.

Gaussian Cgs Unit Of Displacement. Gaussian Cgs Unit Of Magnetization. Gigacoulomb Per Cubic Metre. A grain or troy grain is precisely Gram Of Fissile Isotope. Gram Per Gram. Gram Per Cubic Metre. Gram Per Kilogram. A unit of measurement of mass concentration that shows how many grams of a certain substance are present in one litre. Quantities and units of light and related electromagnetic radiations — Amendment 1.

Quantities and units — Part 6: Light and related electromagnetic radiations. Quantities and units — Part 6: Light and related electromagnetic radiations — Amendment 1. Quantities and units of physical chemistry and molecular physics. Quantities and units of physical chemistry and molecular physics — Amendment 1.

Quantities and units — Part 8: Physical chemistry and molecular physics. Quantities and units — Part 8: Physical chemistry and molecular physics — Amendment 1. Quantities and units of atomic and nuclear physics — Amendment 1. Quantities and units — Part 9: Atomic and nuclear physics — Amendment 1.

Quantities and units of nuclear reactions and ionizing radiations. Quantities and units of nuclear reactions and ionizing radiations — Amendment 1. Quantities and units — Part Nuclear reactions and ionizing radiations.

Quantities and units — Part Nuclear reactions and ionizing radiations — Amendment 1. Mathematical signs and symbols for use in the physical sciences and technology. Quantities and units — Part Mathematical signs and symbols for use in the physical sciences and technology.

Quantities and units — Part Characteristic numbers — Amendment 1. Quantities and units — Part Solid state physics — Amendment 1. SI units and recommendations for the use of their multiples and of certain other units. SI units and recommendations for the use of their multiples and of certain other units — Amendment 1.

Flight dynamics — Concepts, quantities and symbols — Part 1: Aircraft motion relative to the air. Terms and symbols for flight dynamics — Part 2: Motions of the aircraft and the atmosphere relative to the Earth. Flight dynamics — Concepts, quantities and symbols — Part 2: Motions of the aircraft and the atmosphere relative to the Earth.

Flight dynamics — Concepts, quantities and symbols — Part 2: Motions of the aircraft and the atmosphere relative to the Earth — Addendum 1. Terms and symbols for flight dynamics — Part 3: Derivatives of forces, moments and their coefficients.