The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.
Stale discussion now. Feedback forwarded to Lydia in this state. Thanks, John F. Lewis (talk ) 16:42, 27 April 2014 (UTC) [ reply ]
The Wikidata development team is working on the implementation of the quantity datatype (Bugzilla : 54318 ). During this office hour (13.Nov.2013) it was announced that:
Unit conversion will be configurable, but not defined on-wiki. It will draw upon w:GNU Units (see conversion table here ) for reference.
Most probably dimensions (length, speed, etc) will be associated with properties on creation with a configurable default unit (meter, km/h, etc). When setting a value, another unit of the same dimension can be selected.
On the client wikis, it will (eventually) be possible to specify a unit for display, with the software taking care of the appropriate conversion.
Feedback is appreciated on which dimensions and units should be implemented first, and also to detect special cases/needs..
Below there are the dimensions mentioned on "Conversion of units ". The list of properties with dimension awaiting creation also should be integrated into this list. If you think that we should use or not use any of them, leave a comment.
See talk page
SI Prefixes
edit
Metric prefixes
Prefix
Symbol
1000m
10n
Decimal
English word[n 1]
Since[n 2]
yotta
Y
10008
1024
1000 000 000 000 000 000 000 000
septillion
1991
zetta
Z
10007
1021
1000 000 000 000 000 000 000
sextillion
1991
exa
E
10006
1018
1000 000 000 000 000 000
quintillion
1975
peta
P
10005
1015
1000 000 000 000 000
quadrillion
1975
tera
T
10004
1012
1000 000 000 000
trillion
1960
giga
G
10003
109
1000 000 000
billion
1960
mega
M
10002
106
1000 000
million
1960
kilo
k
10001
103
1000
thousand
1795
hecto
h
10002/3
102
100
hundred
1795
deca
da
10001/3
101
10
ten
1795
10000
100
1
one
–
deci
d
1000−1/3
10−1
0.1
tenth
1795
centi
c
1000−2/3
10−2
0.01
hundredth
1795
milli
m
1000−1
10−3
0.001
thousandth
1795
micro
µ
1000−2
10−6
0.000001
millionth
1960
nano
n
1000−3
10−9
0.000000 001
billionth
1960
pico
p
1000−4
10−12
0.000000 000 001
trillionth
1960
femto
f
1000−5
10−15
0.000000 000 000 001
quadrillionth
1964
atto
a
1000−6
10−18
0.000000 000 000 000 001
quintillionth
1964
zepto
z
1000−7
10−21
0.000000 000 000 000 000 001
sextillionth
1991
yocto
y
1000−8
10−24
0.000000 000 000 000 000 000 001
septillionth
1991
↑ This table uses the short scale.
↑ The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the General Conference on Weights and Measures.
Category:Units of length (Q8794341) -- unit of length (Q1978718)
Category:Units of area (Q4393754)
Category:Units of mass (Q7163187)
Spatial dimensions
edit
Category:Units of length (Q8794341) -- unit of length (Q1978718)
For all units including historical or marginal use, see: w:Conversion of units#Length
Category:Units of area (Q4393754)
For all units including historical or marginal use, see: w:Conversion of units#Area
Category:Units of volume (Q7163188)
For all units including historical or marginal use, see: w:Conversion of units#Volume
Plane angle
edit
Category:Units of angle (Q9198409)
metric system (Q232405) of angle (Q11352)
Name of unit
Symbol
Definition
Relation to SI units
radian (Q33680) (SI unit)
rad
The angle subtended at the center of a circle by an arc whose length is equal to the circle's radius. One full revolution encompasses 2π radians.
= 1 rad
milliradian
mrad
≡ 1× 10−3 rad
microradian
μrad
≡ 1× 10−6 rad
nanoradian
nrad
≡ 1× 10−9 rad
picoradian
prad
≡ 1× 10−12 rad
angle (Q11352)
Name of unit
Symbol
Definition
Relation to SI units
milliradian (Q1065153) (NATO)
≡ 2π/6400 rad
≈ 0.981 748× 10−3 rad
arcminute; arcminute (Q209426)
arcmin, amin, am,
′
^
{\displaystyle {\hat {'}}}
, MOA, ( m )
≡ 1°/60
≈ 0.290 888× 10−3 rad
arcsecond; arcsecond (Q829073)
arcsec, asec, as, ( s )
≡ 1°/3600
≈ 4.848 137× 10−6 rad
milliarcsecond
mas
≡ 1 ⁄1,000 arcsecond
≈ 4.8481368 nrad
microarcsecond
μas
≡ 10−6 arcsecond
≈ 4.8481368 prad
degree (Q28390)
°
≡ 1/360 of a revolution ≡ π/180 rad
≈ 17.453 293× 10−3 rad
gradian (Q208528) ; gradian; gon
grad
≡ 1/400 of a revolution ≡ 2π/400 rad ≡ 0.9°
≈ 15.707 963× 10−3 rad
hour angle (Q734439)
( h )
≡ 15°
≡ π ⁄12 rad
turn (Q304479)
rev / rot
≡ 1 revolution ≡ 2π rad
≡ 2π rad
NOTE: degrees-minutes-seconds and hours-minutes-seconds (astronomy) are sometimes combined to represent a value.
For all units including historical or marginal use, see: w:Conversion of units#Plane angle
Solid angle
edit
solid angle (Q208476)
Name of unit
Symbol
Definition
Relation to SI units
millisteradian
msr
= 0.001 sr
square degree (Q254532)
deg²; sq.deg.; (°)²
≡ (π/180)² sr
≈ 0.30462× 10−3 sr
steradian (Q177612) (SI unit)
sr
The solid angle subtended at the center of a sphere of radius r by a portion of the surface of the sphere having an area r2 . A sphere encompasses 4π sr.[9]
= 1 sr
For all units including historical or marginal use, see: w:Conversion of units#Solid angle
Category:Units of mass (Q7163187)
Other units of mass (Q11423)
Name of unit
Symbol
Definition
Relation to SI units
dalton (Q483261)
u; AMU; Da
≈ 1.660 538 73× 10−27 ± 1.3× 10−36 kg
atomic unit of mass, electron rest mass
me
≈ 9.109 382 15× 10−31 ± 45× 10−39 kg [10]
carat (Q261247) (metric)
ct
≡ 200 mg
= 200 mg
Earth mass (Q681996)
M
⊕
{\displaystyle {\begin{smallmatrix}M_{\oplus }\end{smallmatrix}}}
= 5.97219× 1024 kg
electronvolt (Q83327)
eV
≡ 1 eV (energy unit) / c2
= 1.7826× 10−36 kg
ounce (Q48013)
oz av
≡ 1/16 lb
= 28.349 523 125 g
pound (Q100995)
lb av
≡ 0.453 592 37 kg = 7000 grains
≡ 0.453 592 37 kg
solar mass (Q180892)
S /
M
⊙
{\displaystyle {\begin{smallmatrix}M_{\odot }\end{smallmatrix}}}
1.98855 ± 0.00025× 1030 kg
For all units including historical or marginal use, see: w:Conversion of units#Mass
Category:Units of density (Q7210922)
density (Q29539)
Name of unit
Symbol
Definition
Relation to SI units
metric tons per cubic metre
t/m3
≡ t/m3
= 1,000 kg/m3
kilogram per cubic metre (SI unit)
kg/m3
≡ kg/m3
= 1 kg/m3
gram per cubic metre
g/m3
≡ t/m3
= 0.001 kg/m3
kilogram per litre
kg/L
≡ kg/L
=
gram per millilitre
g/mL
≡ g/mL
=
other units of density (Q29539)
Name of unit
Symbol
Definition
Relation to SI units
ounce (avoirdupois) per cubic foot
oz/ft3
≡ oz/ft3
≈ 1.0011 539 61 kg/m3
ounce (avoirdupois) per cubic inch
oz/in3
≡ oz/in3
≈ 1.7299 940 44× 103 kg/m3
ounce (avoirdupois) per gallon (imperial)
oz/gal
≡ oz/gal
≈ 6.2360 232 91 kg/m3
pound (avoirdupois) per cubic foot
lb/ft3
≡ lb/ft3
≈ 16.0184 633 7 kg/m3
pound (avoirdupois) per cubic inch
lb/in3
≡ lb/in3
≈ 2.7679 904 71× 104 kg/m3
pound (avoirdupois) per gallon (imperial)
lb/gal
≡ lb/gal
≈ 99.7763 726 6 kg/m3
For all units including historical or marginal use, see: w:Conversion of units#Density
Category:Units of time (Q8878351)
Second-derived units of time (Q11471)
Name of unit
Symbol
Definition
Relation to SI units
millennium (Q36507) (1000 Julian years)
≡ 1 000 a (see below for definition of year length)
= 1000 years
century (Q578) (100 Julian years)
c
≡ 100 a (see below for definition of year length)
= 100 years
decade (Q39911) (10 Julian years)
dec
≡ 10 a (see below for definition of year length)
= 10 years
Julian year (Q217208)
a, y, or yr
= 365.25 d average, calculated from common years (365 d) plus one leap year (366 d) every four years
= 31 557 600 s
month (Q5151) (30 SI days)
mo
≡ 30 d[11]
= 2 592 000 s
week (Q23387) (7 SI days)
wk
≡ 7 d
= 168 h = 10 080 min = 604 800 s
day (Q573) (24 SI-derived hours)
d
= 24 h
= 1440 min = 86400 s
hour (Q25235) (60 SI-derived minutes)
h
≡ 60 min
= 3 600 s
minute (Q7727) (60 seconds)
min
≡ 60 s
= 60 s
other units of time
Name of unit
Symbol
Definition
Relation to SI units
atomic unit of time
au
≡ a0 /(α·c)
≈ 2.418 884 254× 10−17 s
Planck time (Q202642)
≡ (G ℏ/c 5 )½
≈ 1.351 211 868× 10−43 s
svedberg (Q1472674)
S
≡ 10−13 s
= 100 fs
NOTE: sometimes year-month-day-hours, etc. are combined into a single representation.
Frequency / angular frequency / rotational speed
edit
frequency (Q11652) (as angular frequency (Q834020) )
Name of unit
Symbol
Definition
Relation to SI units
radian per second (Q1063756)
rad·s−1 , rad/s
≡ One unit rpm equals one rotation completed around a fixed axis in one minute of time.
2π rad/sec = 1 Hz
milliradian per second
mrad·s−1 , mrad/s
microradian per second
μrad·s−1 , μrad/s
nanoradian per second
nrad·s−1 , nrad/s
arcsecond per year
arcsec·y−1
milliarcsecond per year
mas·y−1
Mechanics
edit
Speed or velocity
edit
Category:Units of velocity (Q7210890)
A velocity consists of a speed combined with a direction; the speed part of the velocity takes units of speed.
Acceleration
edit
Category:Units of acceleration (Q6456385)
Momentum
edit
momentum (Q41273)
Name of unit
Symbol
Definition
Relation to SI units
kilogram - meter per second
kg m/s
SI unit ≡ kg m/s ≡ N s
Category:Units of force (Q7210873)
See also: Conversion between weight (force) and mass
Pressure or mechanical stress
edit
Category:Units of pressure (Q8890165)
Torque or moment of force
edit
Category:Units of torque (Q7402026)
Category:Units of energy (Q7163185)
energy (Q11379)
Name of unit
Symbol
Definition
Relation to SI units
barrel of oil equivalent
boe
≈ 5.8× 106 BTU59 °F
≈ 6.12× 109 J
British thermal unit (ISO)
BTUISO
≡ 1.0545× 103 J
= 1.0545× 103 J
British thermal unit (International Table)
BTUIT
= 1.055 055 852 62× 103 J
British thermal unit (mean)
BTUmean
≈ 1.055 87× 103 J
British thermal unit (thermochemical)
BTUth
≈ 1.054 350× 103 J
British thermal unit (39 °F)
BTU39 °F
≈ 1.059 67× 103 J
British thermal unit (59 °F)
BTU59 °F
≡ 1.054 804× 103 J
= 1.054 804× 103 J
British thermal unit (60 °F)
BTU60 °F
≈ 1.054 68× 103 J
British thermal unit (63 °F)
BTU63 °F
≈ 1.0546× 103 J
calorie (International Table)
calIT
≡ 4.1868 J
= 4.1868 J
calorie (mean)
calmean
1 ⁄100 of the energy required to warm one gram of air-free water from 0 °C to 100 °C @ 1 atm
≈ 4.190 02 J
calorie (thermochemical)
calth
≡ 4.184 J
= 4.184 J
Calorie (US; FDA )
Cal
≡ 1 kcal
= 1000 cal = 4184 J
calorie (3.98 °C)
cal3.98 °C
≈ 4.2045 J
calorie (15 °C)
cal15 °C
≡ 4.1855 J
= 4.1855 J
calorie (20 °C)
cal20 °C
≈ 4.1819 J
Celsius heat unit (International Table)
CHUIT
≡ 1 BTUIT × 1 K/°R
= 1.899 100 534 716× 103 J
cubic centimetre of atmosphere ; standard cubic centimetre
cc atm; scc
≡ 1 atm × 1 cm3
= 0.101 325 J
cubic foot of atmosphere; standard cubic foot
cu ft atm; scf
≡ 1 atm × 1 ft3
= 2.869 204 480 9344× 103 J
cubic foot of natural gas
≡ 1 000 BTUIT
= 1.055 055 852 62× 106 J
cubic yard of atmosphere; standard cubic yard
cu yd atm; scy
≡ 1 atm × 1 yd3
= 77.468 520 985 2288× 103 J
electronvolt
eV
≡ e × 1 V
≈ 1.602 177 33× 10−19 ± 4.9× 10−26 J
erg (cgs unit )
erg
≡ 1 g·cm2 /s2
= 10−7 J
foot-pound force
ft lbf
≡ g × 1 lb × 1 ft
= 1.355 817 948 331 4004 J
foot-poundal
ft pdl
≡ 1 lb·ft2 /s2
= 4.214 011 009 380 48× 10−2 J
gallon -atmosphere (imperial)
imp gal atm
≡ 1 atm × 1 gal (imp)
= 460.632 569 25 J
gallon-atmosphere (US)
US gal atm
≡ 1 atm × 1 gal (US)
= 383.556 849 0138 J
hartree , atomic unit of energy
Eh
≡ me ·α 2 ·c 2 (= 2 Ry)
≈ 4.359 744× 10−18 J
horsepower-hour
hp·h
≡ 1 hp × 1 h
= 2.684 519 537 696 172 792× 106 J
inch-pound force
in lbf
≡ g × 1 lb × 1 in
= 0.112 984 829 027 6167 J
joule (Q25269) (SI unit)
J
The work done when a force of one newton moves the point of its application a distance of one metre in the direction of the force.[14]
= 1 J = 1 m·N = 1 kg·m2 /s2 = 1 C·V = 1 W·s
kilocalorie; large calorie
kcal; Cal
≡ 1 000 calIT
= 4.1868× 103 J
kilowatt-hour ; Board of Trade Unit
kW·h; B.O.T.U.
≡ 1 kW × 1 h
= 3.6× 106 J
litre -atmosphere
l atm; sl
≡ 1 atm × 1 L
= 101.325 J
quad
≡ 1015 BTUIT
= 1.055 055 852 62× 1018 J
rydberg
Ry
≡ R∞ ·ℎ ·c
≈ 2.179 872× 10−18 J
therm (E.C.)
≡ 100 000 BTUIT
= 105.505 585 262× 106 J
therm (US)
≡ 100 000 BTU59 °F
= 105.4804× 106 J
thermie
th
≡ 1 McalIT
= 4.1868× 106 J
ton of coal equivalent
TCE
≡ 7 Gcalth
= 29.288× 109 J
ton of oil equivalent
TOE
≡ 10 Gcalth
= 41.84× 109 J
ton of TNT
tTNT
≡ 1 Gcalth
= 4.184× 109 J
Power or heat flow rate
edit
power (Q25342) or heat flow rate (Q12160631)
Name of unit
Symbol
Definition
Relation to SI units
atmosphere -cubic centimetre per minute
atm ccm
≡ 1 atm × 1 cm3 /min
= 1.688 75× 10−3 W
atmosphere-cubic centimetre per second
atm ccs
≡ 1 atm × 1 cm3 /s
= 0.101 325 W
atmosphere-cubic foot per hour
atm cfh
≡ 1 atm × 1 cu ft/h
= 0.797 001 244 704 W
atmosphere-cubic foot per minute
atm·cfm
≡ 1 atm × 1 cu ft/min
= 47.820 074 682 24 W
atmosphere-cubic foot per second
atm cfs
≡ 1 atm × 1 cu ft/s
= 2.869 204 480 9344× 103 W
BTU (International Table) per hour
BTUIT /h
≡ 1 BTUIT /h
≈ 0.293 071 W
BTU (International Table) per minute
BTUIT /min
≡ 1 BTUIT /min
≈ 17.584 264 W
BTU (International Table) per second
BTUIT /s
≡ 1 BTUIT /s
= 1.055 055 852 62× 103 W
calorie (International Table) per second
calIT /s
≡ 1 calIT /s
= 4.1868 W
erg per second
erg/s
≡ 1 erg/s
= 10−7 W
foot-pound-force per hour
ft lbf/h
≡ 1 ft lbf/h
≈ 3.766 161× 10−4 W
foot-pound-force per minute
ft lbf/min
≡ 1 ft lbf/min
= 2.259 696 580 552 334× 10−2 W
foot-pound-force per second
ft lbf/s
≡ 1 ft lbf/s
= 1.355 817 948 331 4004 W
horsepower (boiler)
bhp
≈ 34.5 lb/h × 970.3 BTUIT /lb
≈ 9.810 657× 103 W
horsepower (European electrical)
hp
≡ 75 kp·m/s
= 736 W
horsepower (imperial electrical)
hp
≡ 746 W
= 746 W
metric horsepower (Q160857) (imperial mechanical)
hp
≡ 550 ft lbf/s
= 745.699 871 582 270 22 W
metric horsepower (Q160857) (metric)
hp
≡ 75 m kgf/s
= 735.498 75 W
litre -atmosphere per minute
L·atm/min
≡ 1 atm × 1 L/min
= 1.688 75 W
litre-atmosphere per second
L·atm/s
≡ 1 atm × 1 L/s
= 101.325 W
lusec
lusec
≡ 1 L·µmHg/s [9]
≈ 1.333× 10−4 W
poncelet (Q1768929)
p
≡ 100 m kgf/s
= 980.665 W
square foot equivalent direct radiation
sq ft EDR
≡ 240 BTUIT /h
≈ 70.337 057 W
ton of air conditioning
≡ 2000 lbs of ice melted / 24 h
≈ 3 504 W
ton of refrigeration (imperial)
≡ 2240 lb × iceIT / 24 h: iceIT = 144°F × 2326 J/kg.°F
≈ 3.938 875× 103 W
ton of refrigeration (IT)
≡ 200 lbs × iceIT / 24 h: iceIT = 144° × 2326 J/kg.°F
≈ 3.516 853× 103 W
watt (Q25236) (SI unit)
W
The power which in one second of time gives rise to one joule of energy.[14]
= 1 W = 1 J/s = 1 N·m/s = 1 kg·m2 /s3
Flow (volume)
edit
Flow
Name of unit
Symbol
Definition
Relation to SI units
cubic foot per minute
CFM[citation needed ]
≡ 1 ft3 /min
= 4.7194 744 32× 10−4 m3 /s
cubic foot per second
ft3 /s
≡ 1 ft3 /s
= 0.0283 168 465 92 m3 /s
cubic inch per minute
in3 /min
≡ 1 in3 /min
= 2.7311 77 3 × 10−7 m3 /s
cubic inch per second
in3 /s
≡ 1 in3 /s
= 1.6387 064× 10−5 m3 /s
cubic metre per second (SI unit)
m3 /s
≡ 1 m3 /s
= 1 m3 /s
gallon (US fluid) per day
GPD[citation needed ]
≡ 1 gal/d
= 4.3812 636 3 8 × 10−8 m3 /s
gallon (US fluid) per hour
GPH[citation needed ]
≡ 1 gal/h
= 1.0515 032 7 3 × 10−6 m3 /s
gallon (US fluid) per minute
GPM[citation needed ]
≡ 1 gal/min
= 6.3090 196 4× 10−5 m3 /s
litre per minute
LPM[citation needed ]
≡ 1 L/min
= 1.6 × 10−5 m3 /s
Viscosity
edit
Dynamic viscosity
edit
Kinematic viscosity
edit
Electromagnetism
edit
Electric current
edit
Electric charge
edit
Electric dipole
edit
Electric dipole
Name of unit
Symbol
Definition
Relation to SI units
atomic unit of electric dipole moment
e a 0
≈ 8.478 352 81× 10−30 C·m[18]
coulomb meter
C·m
= 1 C · 1 m
debye
D
= 10−10 esu·Å
= 3.33564095× 10−30 C·m [19]
Electromotive force, electric potential difference
edit
Voltage , electromotive force
Name of unit
Symbol
Definition
Relation to SI units
abvolt (cgs unit )
abV
≡ 1× 10−8 V
= 1× 10−8 V
statvolt (cgs unit )
statV
≡ c · (1 μJ/A·m)
= 299.792 458 V
volt (SI unit)
V
The difference in electric potential across two points along a conducting wire carrying one ampere of constant current when the power dissipated between the points equals one watt.[14]
= 1 V = 1 W/A = 1 kg·m2 /(A·s3 )
Electrical resistance
edit
Electrical resistance
Name of unit
Symbol
Definition
Relation to SI units
ohm (Q47083) (SI unit)
Ω
The resistance between two points in a conductor when one volt of electric potential difference, applied to these points, produces one ampere of current in the conductor.[14]
= 1 Ω = 1 V/A = 1 kg·m2 /(A2 ·s3 )
Capacitance
edit
capacitance (Q164399) - ability to store electric charge
Name of unit
Symbol
Definition
Relation to SI units
farad (Q131255) (SI unit)
F
The capacitance between two parallel plates that results in one volt of potential difference when charged by one coulomb of electricity.[14]
= 1 F = 1 C/V = 1 A2 ·s4 /(kg·m2 )
Inductance
edit
inductance (Q177897)
Name of unit
Symbol
Definition
Relation to SI units
henry (Q163354) (SI unit)
H
The inductance of a closed circuit that produces one volt of electromotive force when the current in the circuit varies at a uniform rate of one ampere per second.[14]
= 1 H = 1 Wb/A = 1 kg·m2 /(A·s)2
Magnetic flux
edit
Category:Units of magnetic flux (Q7722730)
magnetic flux (Q177831)
Name of unit
Symbol
Definition
Relation to SI units
maxwell (Q608697) (CGS unit)
Mx
≡ 10−8 Wb[20]
= 1× 10−8 Wb
weber (Q170804) (SI unit)
Wb
Magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.[14]
= 1 Wb = 1 V·s = 1 kg·m2 /(A·s2 )
Magnetic flux density
edit
Category:Units of magnetic flux density (Q7722737)
What physicists call en:Magnetic field is called Magnetic flux density by electrical engineers and magnetic flux density (Q30204) by applied mathematicians and electrical engineers.
Temperature
edit
Category:Units of temperature (Q7210885)
en:Conversion of units of temperature
Information entropy
edit
information entropy (Q204570)
Name of unit
Symbol
Definition
Relation to SI units
Relation to bits
SI unit
J/K
≡ J/K
= 1 J/K
nat ; nip; nepit
nat
≡ kB
= 1.380 650 5(23)× 10−23 J/K
bit (Q8805) ; shannon
bit; b; Sh
≡ ln(2) × kB
= 9.569 940 (16)× 10−24 J/K
= 1 bit
ban ; hartley
ban; Hart
≡ ln(10) × kB
= 3.179 065 3(53)× 10−23 J/K
nibble
≡ 4 bits
= 3.827 976 0(64)× 10−23 J/K
= 22 bit
byte (Q8799)
B
≡ 8 bits
= 7.655 952 (13)× 10−23 J/K
= 23 bit
kilobyte (Q79726) (decimal)
kB
≡ 1 000 B
= 7.655 952 (13)× 10−20 J/K
= 8× 103 bit = 8000 bit
kilobyte (kibibyte )
KB; KiB
≡ 1 024 B
= 7.839 695 (13)× 10−20 J/K
= 213 bit = 8192 bit
Often, information entropy is measured in shannons , whereas the (discrete) storage space of digital devices is measured in bits. Thus, uncompressed redundant data occupy more than one bit of storage per shannon of information entropy. The multiples of a bit listed above are usually used with this meaning. Other times the bit is used as a measure of information entropy and is thus a synonym of shannon.
Lighting
edit
Luminous intensity
edit
The candela is the preferred nomenclature for the SI unit.
luminous intensity (Q104831)
Name of unit
Symbol
Definition
Relation to SI units
candela (Q83216) (SI base unit); candle
cd
The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540× 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.[1]
= 1 cd
candlepower (new)
cp
≡ cd The use of candlepower as a unit is discouraged due to its ambiguity.
= 1 cd
candlepower (old, pre-1948)
cp
Varies and is poorly reproducible.[22] Approximately 0.981 cd.[9]
≈ 0.981 cd
Luminance
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Category:Units of luminance (Q7722791)
Luminous flux
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Category:Units of luminous flux (Q7722767)
Illuminance
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Category:Units of illuminance (Q7722749)
illuminance (Q194411)
Name of unit
Symbol
Definition
Relation to SI units
footcandle ; lumen per square foot
fc
≡ lm/ft2
= 10.7639 104 17 lx
lumen per square inch
lm/in2
≡ lm/in2
≈ 1,550.0031 lx
lux (Q179836) (SI unit)
lx
≡ lm/m2
= 1 lx = 1 lm/m2
phot (Q901492) (CGS unit)
ph
≡ lm/cm2
= 1× 104 lx
Radiation
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Radiation - source activity
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Category:Units of radioactivity (Q7722761)
Please note that although becquerel (Bq) and hertz (Hz) both ultimately refer to the same SI base unit (s−1 ), Hz is used only for periodic phenomena, and Bq is only used for stochastic processes associated with radioactivity.[24]
Radiation - exposure
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Category:Units of radiation dose (Q7163135)
exposure (Q336938) (Radiation - exposure)
Name of unit
Symbol
Definition
Relation to SI units
coulomb per kilogram (SI unit)
C/kg
= 1C / 1kg
roentgen (Q321017) (cgs unit)
R
1 R ≡ 2.58× 10−4 C/kg[20]
= 2.58× 10−4 C/kg
The roentgen is not an SI unit and the NIST strongly discourages its continued use.[25]
Radiation - absorbed dose
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Category:Units of radiation dose (Q7163135)
Radiation - equivalent dose
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Although the definitions for sievert (Sv) and gray (Gy) would seem to indicate that they measure the same quantities, this is not the case. The effect of receiving a certain dose of radiation (given as Gy) is variable and depends on many factors, thus a new unit was needed to denote the biological effectiveness of that dose on the body; this is known as the equivalent dose and is shown in Sv. The general relationship between absorbed dose and equivalent dose can be represented as
H = Q · D
where H is the equivalent dose, D is the absorbed dose, and Q is a dimensionless quality factor. Thus, for any quantity of D measured in Gy, the numerical value for H measured in Sv may be different.[27]
Concentration and chemical composition
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Category:Units of chemical measurement (Q8919525)
Instead of ppm (and similar ppb, ppt) use the correct dimensions (µg/g, ng/g, µl/l) or for numbers without dimensions 10^-6 (or 10^-4 %). Billion and Trillion are not used the same everywhere and the notation is ambiguous because nobody can readily tell what the basis of the ratio (volume, mass, molar) is. --Tobias1984 (talk ) 11:48, 14 November 2013 (UTC) [ reply ]
Thermodynamic units
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Category:Units of chemical measurement (Q8919525)
Name of unit
Symbol
Definition
Relation to SI units
Specific enthalpy (Q161064) (SI-standard)
kJ/mol, kJ/kg
energy per (mass or molar unit)
Specific entropy (Q5380792)
kJ/mol K, kJ/kg K
energy per (mass or molar unit) per kelvin
Specific heat capacity (Q179388)
kJ/mol K, kJ/kg K
energy per (mass or molar unit) per kelvin
Loudness
Name of unit
Symbol
Definition
Relation to SI units
sone (Q676380)
N
Loudness level
Name of unit
Symbol
Definition
Relation to SI units
phon (Q781545)
L_N
Percentage
edit
Currency
edit
Category:Currency (Q6959409)
↑ 1.0 1.1 1.2 1.3 1.4 1.5 The International System of Units, Section 2.1 (8 ed.), Bureau International des Poids et Mesures , 2006, retrieved August 26, 2009
↑ author=jobs url title=The astronomical unit gets fixed : Nature News & Comment doi=10.1038/nature.2012.11416 publisher=Nature.com |date=2012-09-14 |accessdate=2013-08-31
↑ "NIST Reference on Constants, Units, and Uncertainty." (2006). National Institute of Standards and Technology . Retrieved February 22, 2008.
↑ The International Astronomical Union and Astronomical Units
↑ International System of Units, 8th ed. (2006), Bureau International des Poids et Mesures , Section 4.1 Table 8.
↑ P. Kenneth Seidelmann, Ed. (1992). Explanatory Supplement to the Astronomical Almanac. Sausalito, CA: University Science Books. p. 716 and s.v. parsec in Glossary.
↑ Cite error: Invalid <ref>
tag; no text was provided for refs named nbs
↑ Barry N. Taylor, Ed.,NIST Special Publication 330: The International System of Units (SI) (2001 Edition), Washington: US Government Printing Office, 43,"The 12th Conference Generale des Poids et Mesures (CGPM)…declares that the word “litre” may be employed as a special name for the cubic decimetre".
↑ 9.0 9.1 9.2 9.3 Cite error: Invalid <ref>
tag; no text was provided for refs named howmany
↑ CODATA Value: atomic unit of mass. (2006). National Institute of Standards and Technology . Retrieved 16 September 2008.
↑ Pedersen O. (1983). "Glossary" in Coyne, G. , Hoskin, M., and Pedersen, O. Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary . Vatican Observatory. Available from Astrophysics Data System .
↑ Tom Benson. (2010.) "Mach Number" in Beginner's Guide to Aeronautics . NASA .
↑ CODATA Value: atomic unit of force . (2006). National Institute of Standards and Technology . Retrieved September 14, 2008.
↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 Comité International des Poids et Mesures, Resolution 2 , 1946, retrieved August 26, 2009
↑ 15.00 15.01 15.02 15.03 15.04 15.05 15.06 15.07 15.08 15.09 15.10 15.11 15.12 15.13 15.14 15.15 Barry N. Taylor, (April 1 995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: US Government Printing Office, pp. 57–68.
↑ Barry N. Taylor, (April 1995), Guide for the Use of the International System of Units (SI) (NIST Special Publication 811), Washington, DC: US Government Printing Office, p. 5.
↑ International System of Units, 8th ed. (2006), Bureau International des Poids et Mesures , Section 4.1 Table 7.
↑ The NIST Reference on Constants, Units, and Uncertainty , 2006, retrieved August 26, 2009
↑ Robert G. Mortimer Physical chemistry ,Academic Press, 2000 ISBN 0-12-508345-9 , page 677
↑ 20.0 20.1 20.2 NIST Guide to SI Units, Appendix B.9 , retrieved August 27, 2009
↑ Standard for the Use of the International System of Units (SI): The Modern Metric System IEEE/ASTM SI 10-1997. (1997). New York and West Conshohocken, PA: Institute of Electrical and Electronics Engineers and American Society for Testing and Materials . Tables A.1 through A.5.
↑ The NIST Reference on Constants, Units, and Uncertainty , retrieved August 28, 2009
↑ Ambler Thompson & Barry N. Taylor. (2008). Guide for the Use of the International System of Units (SI) . Special Publication 811. Gaithersburg, MD: National Institute of Standards and Technology . p. 10.
↑ 24.0 24.1 The International System of Units, Section 2.2.2., Table 3 (8 ed.), Bureau International des Poids et Mesures , 2006, retrieved August 27, 2009
↑ The NIST Guide to the SI (Special Publication 811), section 5.2 , 2008, retrieved August 27, 2009
↑ Ambler Thompson & Barry N. Taylor. (2008). Guide for the Use of the International System of Units (SI) . Special Publication 811. Gaithersburg, MD: National Institute of Standards and Technology . p. 5.
↑ Comité international des poids et mesures, 2002, Recommendation 2 , retrieved August 27, 2009
Notes
The above discussion is preserved as an archive. Please do not modify it. Subsequent comments should be made in a new section.