Makino EDGE-2, Руководство по предварительной установке, Страница: 108 / 120

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A - 2
A.2 Metric Basics
The first Metric system was established in France after the French Revo-
lution and several systems of metric units have been since developed and
used. All metric systems are partially based on the International Metric
Standards of the Meter and the Kilogram (or decimal multiples and sub-
multiples of these standards).
In 1902 the MKS (meter-kilogram-second) system of units was adopted
and in 1950, the
IEC
adopted the Ampere as a standard unit of measure
resulting in the MKSA (meter, kilogram as a force, second and amp) sys-
tem.
The Conference General des Poids et Mesures (CGPM) of 1954 added
the Kelvin
for temperature and the candela for luminous intensity. These
changes led to the current metric system known as the Systeme Interna-
tional d’Unites
(abbreviated in all languages as SI
)
. The system is continu-
ing to evolve, in 1971, the mole was added as a unit of quantity.
• Though most advanced industrial nations, use a metric system. Most
countries are currently moving away from their system to the SI
system.
All Metric systems are based on decimal arithmetic. This means that for
each physical quantity, units of different sizes are formed by multiplying or
dividing a single base value by powers of 10 (
Table A-1
).
• The metric system is a Base10 system of measurement.
The SI system is both universal and coherent.
• Universality is when there is only one unit for each physical quantity. In
other systems energy may be expressed as; erg, calorie, kilogram
meter, liter atmosphere or horsepower hour. Now it is given in joules.
• A system is coherent, when the product or quotient of any two unit
quantities is the resultant quantity. (i.e. in a system with the foot as the
unit of length, the square foot (not the acre) would be the unit for area.
In summary, the world is moving to the SI system of metric measurement.
However, until this is complete we must be able to convert from other met-
ric systems, the imperial
and U.S
.
system of weights and measures, and
measurements from other sciences.