Baldilocks
New Member
Just an anorak here, turning this one upside down.
My understanding is that the original series (E6) was so that resistors could be made (very badly, with a conductive paint) for a target value (eg 2k). When tested, they could be sorted by their actual values into bins where the values were separated by their tolerances.
Eg: 1k (20%) bin would contain 800R to 1k20
1k5 bin goes from 1k20 to 1k80
2k2 - 1k76 to 2k64
3k3 - 2k64 to 3k96
4k7 - 3k76 to 5k64
6k8 - 5k44 to 8k16
10k - 8k0 up
These values fitted quite well, but when tolerances improved and the E12 values came along, they wanted to keep the E6 values and intersperse the new values - but they didn't quite fit as well as they might have done had they used the equation as guide rather than stay with the already rounded values.
Baldi
My understanding is that the original series (E6) was so that resistors could be made (very badly, with a conductive paint) for a target value (eg 2k). When tested, they could be sorted by their actual values into bins where the values were separated by their tolerances.
Eg: 1k (20%) bin would contain 800R to 1k20
1k5 bin goes from 1k20 to 1k80
2k2 - 1k76 to 2k64
3k3 - 2k64 to 3k96
4k7 - 3k76 to 5k64
6k8 - 5k44 to 8k16
10k - 8k0 up
These values fitted quite well, but when tolerances improved and the E12 values came along, they wanted to keep the E6 values and intersperse the new values - but they didn't quite fit as well as they might have done had they used the equation as guide rather than stay with the already rounded values.
Baldi