E series of preferred numbers


The E series is a system of preferred numbers derived for use in electronic components. It consists of the E3, E6, E12, E24, E48, E96 and E192 series, where the number after the 'E' designates the quantity of logarithmic value "steps" per decade. Although it is theoretically possible to produce components of any value, in practice the need for inventory simplification has led the industry to settle on the E series for resistors, capacitors, inductors, and zener diodes. Other types of electrical components are either specified by the Renard series or are defined in relevant product standards.

History

During the Golden Age of Radio, numerous companies manufactured vacuum-tube–based AM radio receivers for consumer use. In the early years, many components were not standardized between AM radio manufacturers. The capacitance values of capacitors and resistance values of resistors were not standardized as they are today.
In 1924, the Radio Manufacturers Association was formed in Chicago, Illinois by 50 AM radio manufacturers to license and share patents. Over time, this group created some of the earliest standards for electronics components. In 1936, the RMA adopted a preferred-number system for the resistance values of fixed-composition resistors. Over time, resistor manufacturers migrated from older values to the 1936 resistance value standard.
During World War II, American and British military production was a major influence for establishing numerous standards across many industries, especially in electronics, where it was essential to produce high quantities of standardized electronic components to build military devices, such as wireless communications and jammers, radar and jammers, LORAN radio navigation homing receivers for aircraft, ASDIC for submarine navigation and detection, test equipment, and more.
Later, the mid-20th century baby boom and the invention of the transistor kicked off demand for consumer electronics goods during the 1950s. As portable transistor radio manufacturing migrated from United States towards Japan during the late 1950s, it was critical for the electronic industry to have international standards.
After worked on by the RMA, the International Electrotechnical Commission began work on an international standard for preferred values in 1948. The first version of this IEC Publication 63 was released in 1952. Later, IEC 63 was revised, amended, and renamed into the current version known as IEC 60063:2015.
IEC 60063 release history:
  • IEC 63:1952, first edition, published 1952-01-01.
  • IEC 63:1963, second edition, published 1963-01-01.
  • IEC 63:1967/AMD1:1967, first amendment of second edition, published 1967.
  • IEC 63:1977/AMD2:1977, second amendment of second edition, published 1977.
  • IEC 60063:2015, third edition, published 2015-03-27.

    Overview

The E series of preferred numbers was chosen such that when a component is manufactured it will end up in a range of roughly equally spaced values on a logarithmic scale. Each E series subdivides each decade magnitude into steps of 3, 6, 12, 24, 48, 96, and 192 values, termed E3, E6, and so forth to E192, with maximum errors of 40%, 20%, 10%, 5%, 2%, 1%, 0.5%, respectively. Also, the E192 series is used for 0.25% and 0.1% tolerance resistors.
Historically, the E series is split into two major groupings:
  • E3, E6, E12, E24 are subsets of E24. Values in this group are rounded to 2 significant figures.
  • E48, E96, E192 are subsets of E192. Values in this group are rounded to 3 significant figures.

    Formula

The formula for each value is determined by the m-th root, but unfortunately the calculated values don't match the official values of all E series.

E24 subsets

For E3, E6, E12, and E24, the values from the formula are rounded to 2 significant figures, but eight official values are different from the calculated values. During the early half of the 20th century, electronic components had different sets of component values than today. In the late 1940s, standards organizations started working towards codifying a standard set of official component values, and they decided that it wasn't practical to change some of the former established historical values. The first standard was accepted in Paris in 1950, then published as IEC 63 in 1952. The official values of the E3, E6, and E12 series are subsets of the following official E24 values.
The E3 series is rarely used, except for some components with high variations like electrolytic capacitors, where the given tolerance is often unbalanced between negative and positive such as or, or for components with uncritical values such as pull-up resistors. The calculated constant tangential tolerance for this series gives ÷ = 36.60%, approximately. While the standard only specifies a tolerance greater than 20%, other sources indicate 40% or 50%. Currently, most electrolytic capacitors are manufactured with values in the E6 or E12 series, thus E3 series is mostly obsolete.

E192 subsets

For E48, E96, and E192, the values from the formula are rounded to 3 significant figures, but one value is different from the calculated values.
  • To calculate the E48 series: is 48, then is incremented from 0 to 47 through the formula. All official values of E48 series match their calculated values.
  • To calculate the E96 series: is 96, then is incremented from 0 to 95 through the formula. All official values of E96 series match their calculated values.
  • To calculate the E192 series: is 192, then is incremented from 0 to 191 through the formula, with one exception for where 9.20 is the official value instead of the calculated 9.19 value.
Since some values of the E24 series do not exist in the E48, E96, or E192 series, some resistor manufacturers have added missing E24 values into of their 1%, 0.5%, 0.25%, 0.1% tolerance resistor families. This allows easier purchasing migration between various tolerances. This E series merging is noted on resistor datasheets and webpages as "E96 + E24" or "E192 + E24". In the following table, the red cells denote E24 values that don't exist in the E48, E96, or E192 series, and indicate the closest value or values that do instead.

Examples

If a manufacturer sold resistors with all values in a range of 1 ohm to 10 megaohms, the available resistance values for E3 through E12 would be:
  • 1.0, 2.2, 4.7,
  • 10, 22, 47,
  • 100, 220, 470,
  • 1 k, 2.2 k, 4.7 k,
  • 10 k, 22 k, 47 k,
  • 100 k, 220 k, 470 k,
  • 1 M, 2.2 M, 4.7 M,
  • 10 M
  • 1.0, 1.5, 2.2, 3.3, 4.7, 6.8,
  • 10, 15, 22, 33, 47, 68,
  • 100, 150, 220, 330, 470, 680,
  • 1 k, 1.5 k, 2.2 k, 3.3 k, 4.7 k, 6.8 k,
  • 10 k, 15 k, 22 k, 33 k, 47 k, 68 k,
  • 100 k, 150 k, 220 k, 330 k, 470 k, 680 k,
  • 1 M, 1.5 M, 2.2 M, 3.3 M, 4.7 M, 6.8 M,
  • 10 M
  • 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2,
  • 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82,
  • 100, 120, 150, 180, 220, 270, 330, 390, 470, 560, 680, 820,
  • 1 k, 1.2 k, 1.5 k, 1.8 k, 2.2 k, 2.7 k, 3.3 k, 3.9 k, 4.7 k, 5.6 k, 6.8 k, 8.2 k,
  • 10 k, 12 k, 15 k, 18 k, 22 k, 27 k, 33 k, 39 k, 47 k, 56 k, 68 k, 82 k,
  • 100 k, 120 k, 150 k, 180 k, 220 k, 270 k, 330 k, 390 k, 470 k, 560 k, 680 k, 820 k,
  • 1 M, 1.2 M, 1.5 M, 1.8 M, 2.2 M, 2.7 M, 3.3 M, 3.9 M, 4.7 M, 5.6 M, 6.8 M, 8.2 M,
  • 10 M
If a manufacturer sold capacitors with all values in a range of 1 pF to 10,000 μF, the available capacitance values for E3 and E6 would be:
  • 1.0 pF, 2.2 pF, 4.7 pF,
  • 10 pF, 22 pF, 47 pF,
  • 100 pF, 220 pF, 470 pF,
  • 1 nF, 2.2 nF, 4.7 nF,
  • 10 nF, 22 nF, 47 nF,
  • 100 nF, 220 nF, 470 nF,
  • 1 μF, 2.2 μF, 4.7 μF,
  • 10 μF, 22 μF, 47 μF,
  • 100 μF, 220 μF, 470 μF,
  • 1000 μF, 2200 μF, 4700 μF,
  • 10000 μF
  • 1.0 pF, 1.5 pF, 2.2 pF, 3.3 pF, 4.7 pF, 6.8 pF,
  • 10 pF, 15 pF, 22 pF, 33 pF, 47 pF, 68 pF,
  • 100 pF, 150 pF, 220 pF, 330 pF, 470 pF, 680 pF,
  • 1 nF, 1.5 nF, 2.2 nF, 3.3 nF, 4.7 nF, 6.8 nF,
  • 10 nF, 15 nF, 22 nF, 33 nF, 47 nF, 68 nF,
  • 100 nF, 150 nF, 220 nF, 330 nF, 470 nF, 680 nF,
  • 1 μF, 1.5 μF, 2.2 μF, 3.3 μF, 4.7 μF, 6.8 μF,
  • 10 μF, 15 μF, 22 μF, 33 μF, 47 μF, 68 μF,
  • 100 μF, 150 μF, 220 μF, 330 μF, 470 μF, 680 μF,
  • 1000 μF, 1500 μF, 2200 μF, 3300 μF, 4700 μF, 6800 μF,
  • 10000 μF

    Lists

List of official values for each E series:
;E3 values
;E6 values
;E12 values
;E24 values
;E48 values
;E96 values
;E192 values

Table