Preferred Number Series for Resistors and Capacitors
|Publication Date:||1 March 2015|
|ICS Code (Capacitors):||31.060|
|ICS Code (Resistors):||31.040|
This International Standard provides series of preferred values for the resistance of resistors and for the capacitance of capacitors.
The definition of such series with a defined numeric resolution is a basic prerequisite for the marking and coding of capacitors and resistors with their respective capacitance or resistance values as described in IEC 60062.
NOTE The number series defined in this standard are based on progressive ratios of r√10 , with r = 3 · 2i, and i being a whole number in the range of 0 to 6, hence e.g. of 12√10 .
This system of progressive ratios had been established prior to the 1952 release of the first edition of this standard1 as a consequence of the standardisation of tolerances at ±5 %, ±10 % and ±20 % and the related commercial practice. An adoption of the ISO practice, based on a 10√10 system, was never considered achievable.