Preferred number series for resistors and capacitors

2Scope / Description

This international standard provides a series of preferred numerical values for the resistance of resistors and the capacitance of capacitors. This definition of a series with defined numerical resolution is a fundamental premise for marking and coding capacitors and resistors with their respective capacitance or resistance values, as described in IEC 60062. Note: The numerical series defined in this standard is based on a progressive ratio of 10^(1/r), where r = 3 · 2^i, and i is an integer in the range of 0 to 6, for example, 12^(1/10). This progressive ratio system was established prior to the initial publication of this standard in 1952, as a result of the standardization of tolerances of ±5%, ±10%, and ±20% and related commercial practices. The adoption of ISO practices based on the 10^(1/10) system was never considered feasible.