System International (SI) Notation
Article : Andy Collinson
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Overview:
Many of the schematics on this site have parts that are labeled using the System International (SI) notation system. The SI system is an easy way to describe values without the need for a decimal point. Circuits that have been previously drafted on paper may have a decimal point that has faded or hard to see. The SI system thereby overcomes this problem and offers a clear advantage. Multipliers are used in the SI system, taking the place of the decimal point in the conventional naming system.

The following table indicates the multipliers for the commonest values used in electronics:-

Table of Multipliers
NumberPrefixSymbol
10 12teraT
10 9gigaG
10 6megaM
10 3kilok
10 -3millim
10 -6microu
10 -9nanon
10 -12picop
Using SI notation the unit of measurement appears at the end of the value. Resistor values are in ohms (R), capacitance is measured in farads (F) and inductors are measured in Henrys (H). So a 10 ohm resistor would be wrote as 10R and a 4.7mH inductor 4m7H. Usually the end letter is omitted. More examples:-

2.2k = 2k2

4.7k = 4k7

2.5A = 2A5

.0015u = 1.5n =1n5