1. Areas
     Mechanics    Thermodynamics    Electromagnetism    Light    Acoustics    Information science and technology    Other areas  

2. International System of Quantities

3. Units of the ISO and IEC 80000 series

4. See also

5. References

6. External links

ISO 80000 or IEC 80000 is an international standard promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

The standard introduces the International System of Quantities (ISQ). It is a style guide for the use of physical quantities and units of measurement, formulas involving them, and their corresponding units, in scientific and educational documents for worldwide use. In most countries, the notations used in mathematics and science textbooks at schools and universities follow closely the guidelines in this standard.{{Citation needed|date=October 2016}}

The ISO/IEC 80000 family of standards was completed with the publication of Part 1 in November 2009.^[1]

Areas

The 80000 standard currently has 14 parts.^[2]

Mechanics

ISO 80000-4:2006 supersedes ISO 31-3.^[3] and specifies names and symbols for quantities and units of classical mechanics, and defines these names and symbols. The document is under review.^[4]

Thermodynamics

ISO 80000-5:2007 supersedes ISO 31-4^[5] which "gives names, symbols and definitions for quantities and units of thermodynamics". The document is under review.^[6]

Electromagnetism

IEC 80000-6:2008 supersedes ISO 31-5^[7] as well as IEC 60027-1, and specifies names and symbols for quantities and units related to electromagnetism, and defines these quantities and units.

Light

ISO 80000-7:2008 supersedes ISO 31-6,^[8] and specifies names and symbols to quantities and units for light and other electromagnetic radiation, and defines these quantities and units. The document is under review.^[9]

Acoustics

ISO 80000-8:2007 specifies names, symbols for quantities and units of acoustics and provides definitions for these quantities and units. It supersedes ISO 31-7^[10] and is under review.^[11] It has a foreword; introduction; scope; normative references; and names, symbols and definitions. The standard includes definitions of sound pressure, sound power and sound exposure, and their corresponding levels: sound pressure level, sound power level and sound exposure level. For example:

• period duration (symbol T): duration of one cycle of a periodic phenomenon
• frequency (symbol f): f = 1/T
• logarithmic frequency interval (symbol G): G = lb(f₂/f₁)
• angular frequency (symbol ω): ω = 2πf
• wavelength (symbol λ): for a sinusoidal wave and in a direction perpendicular to the wavefront, distance between two successive points where at a given instant the phase ... differs by 2 π
• wavenumber (symbol σ): σ = 1/λ
• angular wavenumber (symbol k): k = ω/c
• density (symbol ρ): ρ = m/V
• static pressure (symbol p_s): pressure that would exist in the absence of sound waves
• sound pressure (symbol p): difference between instantaneous total pressure and static pressure
• sound particle displacement (symbol δ): instantaneous displacement of a particle in a medium from what would be its position in the absence of sound waves
• sound particle velocity (symbol v,u): v = dδ/dt
• sound particle acceleration (symbol a): a = dv/dt
• sound volume velocity (symbol q): surface integral of the normal component of the sound particle velocity ... over the cross-section (through which the sound propagates)
• phase speed of sound (symbol c): c = ω/k
• group speed of sound (symbol c_g): c_g = dω/dk
• sound energy density (symbol w): time-averaged sound energy in a given volume divided by that volume
• sound power (symbol P, P_a): through a surface, product of the sound pressure ... and the component of the particle velocity ... at a point on the surface in the direction normal to the surface, integrated over that surface
• sound intensity (symbol i): i = p.v
• time-averaged sound intensity (symbol I):
• sound exposure (symbol E):
• characteristic impedance of a medium (symbol Z_c): at a point in a non-dissipative medium and for a plane progressive wave, the quotient of the sound pressure ... by the component of the sound particle velocity ... in the direction of the wave propagation
• acoustic impedance (symbol Z_a): at a surface, the complex quotient of the average sound pressure ... over that surface by the sound volume flow rate ... through that surface
• mechanical surface impedance (symbol Z_m): at a surface, the complex quotient of the total force on the surface by the component of the average sound particle velocity ... at the surface in the direction of the force
• sound pressure level (symbol L_p):
• sound power level (symbol L_W):
• sound exposure level (symbol L_E):
• attenuation coefficient (symbol α):
• phase coefficient (symbol β):
• propagation coefficient (symbol γ):
• dissipation factor for sound power (symbol δ, ψ):
• reflection factor for sound power (symbol r):
• transmission factor for sound power (symbol τ):
• absorption factor for sound power (symbol α):
• sound reduction index (symbol R):
• equivalent absorption area of a surface or object (symbol A):
• reverberation time (symbol T_n):

Information science and technology

IEC 80000-13:2008 defines quantities and units used in information science, and specifies names and symbols for these quantities and units.^[12] The current edition was published in 2008, and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 and IEC 60027-3. It has a scope; normative references; names, definitions and symbols; and prefixes for binary multiples. Quantities defined in this standard are:

• traffic intensity [A]: number of simultaneously busy resources in a particular pool of resources
• traffic offered intensity [A₀]: traffic intensity ... of the traffic that would have been generated by the users of a pool of resources if their use had not been limited by the size of the pool
• traffic carried intensity [Y]: traffic intensity ... of the traffic served by a particular pool of resources
• mean queue length [L, (Ω)]: time average of queue length
• loss probability [B]: probability for losing a call attempt
• waiting probability [W]: probability for waiting for a resource
• call intensity, calling rate [λ]: number of call attempts over a specified time interval divided by the duration (ISO 80000-3 ...) of this interval
• completed call intensity [μ]: call intensity ... for the call attempts that result in the transmission of an answer signal
• storage capacity, storage size [M]
• equivalent binary storage capacity [M_e]
• transfer rate [r, (ν)]
• period of data elements [T]
• binary digit rate, bit rate [r_b, r_bit (ν_b, ν_bit)]
• period of binary digits, bit period [T_b, T_bit]
• equivalent binary digit rate, equivalent bit rate [r_e, (ν_e)]
• modulation rate, line digit rate [r_m, u]
• quantizing distortion power [T_Q]
• carrier power [P_c, C]
• signal energy per binary digit [E_b, E_bit]
• error probability [P]
• Hamming distance [d_n]
• clock frequency, clock rate [f_cl]
• decision content [D_a]
• information content [I(x)]
• entropy [H]
• maximum entropy [H₀, (H_max)]
• relative entropy [H_r]
• redundancy [R]
• relative redundancy [r]
• joint information content [I(x, y)]
• conditional information content [I(x|y)]
• conditional entropy, mean conditional information content, average conditional information content [H(X|Y)]
• equivocation [H(X∣Y)]
• irrelevance [C]
• transinformation content [T(x, y)]
• mean transinformation content [T]
• character mean entropy [H′]
• average information rate [H]
• character mean transinformation content [T′]
• average transinformation rate [T]
• channel capacity per character; channel capacity [C′]
• channel time capacity; channel capacity [C]

The Standard also includes definitions for units relating to information technology, such as the erlang (symbol E), bit (bit), octet (o), byte (B), baud (Bd), shannon (Sh), hartley (Hart) and the natural unit of information (nat).

Clause 4 of the Standard defines standard binary prefixes used to denote powers of 1024 as 1024¹ (kibi-), 1024² (mebi-), 1024³ (gibi-), 1024⁴ (tebi-), 1024⁵ (pebi-), 1024⁶ (exbi-), 1024⁷ (zebi-) and 1024⁸ (yobi-).

Other areas

International System of Quantities

Part 1 of ISO 80000 introduces the International System of Quantities and describes its relationship with the International System of Units (SI). Specifically, its introduction states "The system of quantities, including the relations among the quantities used as the basis of the units of the SI, is named the International System of Quantities, denoted 'ISQ', in all languages.", and further clarifies that "ISQ is simply a convenient notation to assign to the essentially infinite and continually evolving and expanding system of quantities and equations on which all of modern science and technology rests".

Units of the ISO and IEC 80000 series

The standard includes all SI units but is not limited to only SI units. Units that form part of the standard but not the SI include the units of information storage (bit and byte), units of entropy (shannon, natural unit of information and hartley), the erlang (a unit of traffic intensity) and units of level (neper and decibel). The standard includes all SI prefixes as well as the binary prefixes kibi-, mebi-, gibi-, etc., originally introduced by the International Electrotechnical Commission to standardise binary multiples of byte such as mebibyte (MiB), for {{val|1024}}² bytes, to distinguish them from their decimal counterparts such as megabyte (MB), for precisely one million ({{val|1000}}²) bytes. In the standard, the application of the binary prefixes is not limited to units of information storage. For example, a frequency ten octaves above one hertz, i.e., 2¹⁰ Hz ({{val|1024|u=Hz}}), is one kibihertz (1 KiHz).

These binary prefixes were standardized first in a 1999 addendum to IEC 60027-2.

The harmonized IEC 80000-13:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005, which had defined the prefixes for binary multiples. The only significant change in IEC 80000-13 is the addition of explicit definitions for some quantities.

See also

• International Vocabulary of Metrology
• International System of Units
• BIPM – publishes freely available information on SI units
• NIST – official U.S. representative for SI; publishes freely available guide to use of SI

References

External links

• BIPM SI Brochure
• ISO TC12 standards – Quantities, units, symbols, conversion factors
• NIST Special Publication 330 – The International System of Units
• NIST Special Publication 811 – Guide for the Use of the International System of Units

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