3 ms·

The reason is clearly outlined on the wikipedia page: https://en.wikipedia.org/wiki/E_series_of_preferred_numbers https://en.wikipedia.org/wiki/E_series_of_pref

The reason is clearly outlined on the wikipedia page: https://en.wikipedia.org/wiki/E_series_of_preferred_numbers https://en.wikipedia.org/wiki/E_series_of_preferred_numbers > Since the electronic component industry established component values before standards discussions in the late-1940s, they decided that it wasn't practical to change the former established values. These older values were used to create the E6, E12, E24 series standard that was accepted in Paris in 1950 then published as IEC 63 in 1952.

jefftk 4y ago
That's not much of a reason: why were the older values chosen? The article looks back and argues that it was to make more unique values possible.
- svnt 4y ago
  They were probably chosen because the decision was made in concert with manufacturers who wanted to be able to continue to buy/build with the values they had before. I’m surprised so many here are taking issue with the answer on the page. It’s a reasonable answer reflecting a pragmatic process. Just don’t rug-pull our existing components and give us more variation. And don’t give me “you can get odd numbers with two resistors” — at the time this was done, these things were not cheap, they were not small, and doubling your component count and increasing your product size because of a new government standard would not have gone over well.
- deleted 4y ago
  [deleted]
- threatripper 4y ago
  You can ask that question, too - but it's irrelevant to the question why the E12 series was changed in this way.
  - hgsgm 4y ago
    The original question was why E12 10^(n/12) was misrounded. The wikipedia page only explains why the E system was E12 inatead of E10.
- adql 4y ago
  That seems the same problem of "why train track spacing is like it is" and the answer is "nothing actually technical". 1,2,5 series woud've been much more useful considering how often in electronics you need integer ratio of some 2 values
  - ted_dunning 4y ago
    Well, the 1, 2.2, 4.7 E3 sequence that is embedded in the E12 sequence is plenty close enough for almost all applications. The successive ratios are noticeably more consistent than for the 1,2,5,10 sequence (2.2, 2.14, 2.13 versus 2, 2.5, 2)

jefftk 4y ago

That's not much of a reason: why were the older values chosen? The article looks back and argues that it was to make more unique values possible.

svnt 4y ago
They were probably chosen because the decision was made in concert with manufacturers who wanted to be able to continue to buy/build with the values they had before. I’m surprised so many here are taking issue with the answer on the page. It’s a reasonable answer reflecting a pragmatic process. Just don’t rug-pull our existing components and give us more variation. And don’t give me “you can get odd numbers with two resistors” — at the time this was done, these things were not cheap, they were not small, and doubling your component count and increasing your product size because of a new government standard would not have gone over well.
deleted 4y ago
[deleted]
threatripper 4y ago
You can ask that question, too - but it's irrelevant to the question why the E12 series was changed in this way.
- hgsgm 4y ago
  The original question was why E12 10^(n/12) was misrounded. The wikipedia page only explains why the E system was E12 inatead of E10.
adql 4y ago
That seems the same problem of "why train track spacing is like it is" and the answer is "nothing actually technical". 1,2,5 series woud've been much more useful considering how often in electronics you need integer ratio of some 2 values
- ted_dunning 4y ago
  Well, the 1, 2.2, 4.7 E3 sequence that is embedded in the E12 sequence is plenty close enough for almost all applications. The successive ratios are noticeably more consistent than for the 1,2,5,10 sequence (2.2, 2.14, 2.13 versus 2, 2.5, 2)