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Units of measurement

The basic idea from which the metric system has originated - a system of units based on the meter and the kilogram - was created during the French Revolution when the first two reference standards were made - for meter and kilogram, made of platinum, and then located in the French National Archives in Paris in 1799 . – which is how they later became known as the archive meter and the archive kilogram. French National Assembly then ordered the French Academy of Sciences to develop a new system of units that would be used throughout the world, and in 1946, the Member States of the Metre Convention accepted MKSA (meter, kilogram, second, ampere) system. In 1954 MKSA system was expanded by including kelvin and candela. The system was definitely named the International System of Units, SI, (Le Système International d'Unités) then. International System of Units SI was established in 1960 at the 11th General Conference on Weights and Measures (CGPM - Conférence Générale des Poids et Mesures).

"International System of Units, SI, is a coherent system of units adopted and recommended by the General Conference on Weights and Measures (CGPM)."

At the 14th CGPM in 1971. SI was again extended by adding the mole  as the base unit for amount of substance. Now SI system consists of seven base units, which together with derived units make the coherent system of units. Due to the widespread use or for the use in specific areas of application, the use of the units outside the SI is also accepted.

SI BASE UNITS:

Quantity
Base Unit
Symbol
lenght
meter
m
mass
kilogram
kg
time
second
s
electrical curent
ampere
A
thermodynamic temperature
kelvin
K
amount of substance
mol
mol
luminous intensity
candela
c d

 

 

 

 

  

 

 

CGPM has adopted and recommended a series of prefixes and their symbols.

Factor
Prefix name
Symbol
Factor
Prefix name
Symbol
101
deka
da
10-1
deci
d
102
hecto
h
10-2
centi
c
103
kilo
k
10-3
milli
m
106
mega
M
10-6
mikro
µ
109
giga
G
10-9
nano
n
1012
tera
T
10-12
piko
p
1015
peta
P
10-15
femto
f
1018
eksa
E
10-18
atto
a
1021
zetta
Z
10-21
zepto
z
1024
jotta
Y
10-24
yokto
y