Database units are used for storing data in the databases. All database units are stored in the International System (SI) of units. SI is the accepted units system of the International Organization for Standardization (ISO).
Base Database Units
A base unit is dimensionally independent of all other unit types. Every system of units contains nine base units: distance, angle, mass, time, temperature, charge, luminous intensity, amount of a substance, and solid angle.
Unit Type |
D |
A |
M |
Ti |
Te |
C |
L |
As |
Sa |
Base Unit |
Identifier |
---|---|---|---|---|---|---|---|---|---|---|---|
Distance (D) |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
meter |
m |
Angle (A) |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
radian |
rad |
Mass (M) |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
kilogram |
kg |
Time (Ti) |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
second |
s |
Temperature (Te) |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
Kelvin |
K |
Charge (C) |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
ampere |
A |
Luminous Intensity (L) |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
candela |
cd |
Amount of Substance (As) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
mole |
mol |
Solid Angle (Sa) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
steradian |
sr |
All other SI units are derived and stored as a combination of these units. For non-SI units, conversion factors are provided to convert the unit to the appropriate combination of the database base units. For example, the area unit is always converted and stored as the square of the base distance unit meter (m2). If an area input is given as in2, the value is scaled by the appropriate conversion factor and stored in m2.
Derived Database Units
Derived units are defined in terms of a combination of the base units. Because the system performs a dimensional analysis when data is input to the system, the database derived units must be unique. For example, pressure and stress are both defined in terms of the same base unit combination (kg/m•s2); therefore, both cannot exist as a derived database unit. In this case, the more generic unit, force per unit area, is used to satisfy both the pressure and stress unit.
Unit Type |
D |
A |
M |
Ti |
Te |
C |
L |
As |
Sa |
Base Unit |
Common |
---|---|---|---|---|---|---|---|---|---|---|---|
Angular acceleration |
0 |
1 |
0 |
-2 |
0 |
0 |
0 |
0 |
0 |
rad/s2 |
|
Angular momentum |
1 |
0 |
2 |
-1 |
0 |
0 |
0 |
0 |
0 |
kg•m2/s |
|
Angular velocity |
0 |
1 |
0 |
-1 |
0 |
0 |
0 |
0 |
0 |
rad/s |
|
Area |
0 |
2 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
m2 |
|
Body force |
-2 |
0 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg/m2•s2 |
N/m3 |
Coefficient of thermal expansion |
0 |
0 |
0 |
0 |
-1 |
0 |
0 |
0 |
0 |
/°K |
|
Density |
-3 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
kg/m3 |
|
Electrical capacitance |
-2 |
0 |
-1 |
4 |
0 |
2 |
0 |
0 |
0 |
A2•s4(kg•m2) |
A•s/V, C/V, or Farad (F) |
Electrical Conductance |
-2 |
0 |
-1 |
3 |
0 |
2 |
0 |
0 |
0 |
A2•s3/(kg•m2) |
A/V or Siemens (S) |
Electrical conductivity |
1 |
0 |
1 |
-3 |
0 |
-2 |
0 |
0 |
0 |
kg•m/(s3•A2) |
|
Electrical field strength |
1 |
0 |
1 |
-3 |
0 |
-1 |
0 |
0 |
0 |
kg•m/(s3•A) |
V/m |
Electrical inductance |
2 |
0 |
1 |
-2 |
0 |
-2 |
0 |
0 |
0 |
kg•m2/(s2•A2) |
V•s/A or Henry (H) |
Electrical potential difference |
2 |
0 |
1 |
-3 |
0 |
-1 |
0 |
0 |
0 |
kg•m2/(s3•A) |
W/AVolt (V) |
Electrical resistance |
2 |
0 |
1 |
-3 |
0 |
-2 |
0 |
0 |
0 |
kg•m2/(s3•A2) |
V/A, ohm, or W |
Energy |
2 |
0 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg•m2/s2 |
N•m or Joule (J) |
Enthropy |
2 |
0 |
1 |
-2 |
-1 |
0 |
0 |
0 |
0 |
kg•m2/(s2•°K) |
J/°K |
Film coefficient (heat transfer) |
0 |
0 |
1 |
-3 |
-1 |
0 |
0 |
0 |
0 |
kg/(s3•°K) |
W/m2•°K |
Force |
1 |
0 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg•m/s2 |
Newton (N) |
Force per area |
-1 |
0 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg/m•s2 |
N/m2 or Pascal (Pa) |
Force per distance |
0 |
0 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg/s2 |
N/m |
Frequency |
0 |
0 |
0 |
-1 |
0 |
0 |
0 |
0 |
0 |
1/s |
Hertz (Hz) |
Heat capacity |
2 |
0 |
0 |
-2 |
-1 |
0 |
0 |
0 |
0 |
m2/(s2•°K) |
J/kg•°K |
Heat flux per area |
0 |
0 |
1 |
-3 |
0 |
0 |
0 |
0 |
0 |
kg/s3 |
W/m2 |
Heat flux per distance |
1 |
0 |
1 |
-3 |
0 |
0 |
0 |
0 |
0 |
kg•m/s3 |
W/m |
Heat source |
-1 |
0 |
1 |
-3 |
0 |
0 |
0 |
0 |
0 |
kg/(m•s3) |
W/m3 |
Illuminance |
-2 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
cd•sr/m2 |
lux or lx |
Linear acceleration |
1 |
0 |
0 |
-2 |
0 |
0 |
0 |
0 |
0 |
m/s2 |
|
Linear per angular |
1 |
-1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
m/rad |
|
Linear velocity |
1 |
0 |
0 |
-1 |
0 |
0 |
0 |
0 |
0 |
m/s |
|
Luminous flux |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
cd•sr |
lumen or lm |
Magnetic field strength |
-1 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
A/m |
|
Magnetic flux |
2 |
0 |
1 |
-2 |
0 |
-1 |
0 |
0 |
0 |
kg•m2/(s2•A) |
V•s or Weber (Wb) |
Magnetic flux density |
0 |
0 |
1 |
-2 |
0 |
-1 |
0 |
0 |
0 |
kg/(s2•A) |
Wb/m2 or Tesla (T) |
Mass flow rate |
0 |
0 |
1 |
-1 |
0 |
0 |
0 |
0 |
0 |
kg/s |
|
Mass moment of inertia |
2 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
kg•m2 |
|
Mass per area |
-2 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
kg/m2 |
|
Mass per length |
-1 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
kg/m |
|
Momentum |
1 |
0 |
1 |
-1 |
0 |
0 |
0 |
0 |
0 |
kg•m/s |
|
Per distance |
-1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
/m |
|
Power |
2 |
0 |
1 |
-3 |
0 |
0 |
0 |
0 |
0 |
kg•m2/s3 |
Watt |
Quantity of electricity |
0 |
0 |
0 |
1 |
0 |
1 |
0 |
0 |
0 |
A•s |
A•s Coulomb (C) |
Radiant intensity |
2 |
0 |
1 |
-3 |
0 |
0 |
0 |
0 |
-1 |
kg•m2/(s3•sr) |
W/sr |
Rotational stiffness |
2 |
-1 |
1 |
-2 |
0 |
0 |
0 |
0 |
0 |
kg•m2/(s2•rad) |
N•m/rad |
Second moment of area |
4 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
m4 |
|
Thermal conductivity |
1 |
0 |
1 |
-3 |
-1 |
0 |
0 |
0 |
0 |
kg•m/(s3•°K) |
W/(m•°K) |
Viscosity (dynamic) |
-1 |
0 |
1 |
-1 |
0 |
0 |
0 |
0 |
0 |
kg/(m•s) |
N•s/m2 or Pa•s |
Viscosity (kinematic) |
2 |
0 |
0 |
-1 |
0 |
0 |
0 |
0 |
0 |
m2/s |
|
Volume |
3 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
m3 |
|
Volume flow rate |
3 |
0 |
0 |
-1 |
0 |
0 |
0 |
0 |
0 |
m3/s |