Examples of
internationally
agreed exceptions
Time
Time uses an older internationally agreed system.
| Name | Symbol | Quantity | Equivalent SI unit |
|
minute |
min | time | 1 min = 60 s |
|
hour |
h |
time | 1 h = 3600 s |
|
day |
d |
time | 1 d = 86400 s |
Angle
In dimensional metrology you may also have to measure angle. Angle has its own set of units. The SI unit of angle is the radian.
| Name | Symbol | Quantity | Equivalent SI unit |
|
degree of arc |
° | angle | 1° = (π/180) rad |
|
minute of arc |
' |
angle | 1' = (π/10800) rad |
|
second of arc |
" |
angle | 1" = (π/648000) rad |
|
hectare |
ha |
area | 1 ha = 10000 m2 |
|
litre |
l or L |
volume | 1 l = 0.001 m3 |
|
tonne |
t |
mass | 1 t = 1000 kg |
Ionising radiation
In the field of ionising radiation, the SI unit of activity is the Becquerel, and the SI units of absorbed dose and dose equivalent are the gray and sievert, respectively. These names were introduced because of the dangers to human health that might arise from mistakes involving the reciprocal second and joule per kilogram.
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