jims99
Electrical
- Sep 11, 2003
- 19
We all know the standard (5%, 10%, or 20%) EIA resistor values. For example, the E12 series (10%) are 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82.
These values were supposed to have been derived from the mathematical series of equally spacing values logarithmically for each decade(*). When calculating to arrive to values, we get following (rounded off to 2 significant digits: 10, 12, 15, 18, 22, 26, 32, 38, 47, 56, 68 and 83. Note the discrepancy for 5 out of 12 values (26, 32, 38, 46, 83) from actual used values. (BTW: the 1% series values, E96, are correct!)
Can anyone shed light on this (mistake?). Did someone goof around the turn of the century?
---Jim
(*) For E12 series: k=10^(1/12)= 1.2115277
Values are then: k^n (n=0,…,11)
These values were supposed to have been derived from the mathematical series of equally spacing values logarithmically for each decade(*). When calculating to arrive to values, we get following (rounded off to 2 significant digits: 10, 12, 15, 18, 22, 26, 32, 38, 47, 56, 68 and 83. Note the discrepancy for 5 out of 12 values (26, 32, 38, 46, 83) from actual used values. (BTW: the 1% series values, E96, are correct!)
Can anyone shed light on this (mistake?). Did someone goof around the turn of the century?
---Jim
(*) For E12 series: k=10^(1/12)= 1.2115277
Values are then: k^n (n=0,…,11)
