Make: Online : EIA resistor values explained

EIA resistor values explained

Jeff, he of the mightyOhm, asks:

Have you ever wondered why standard 5% resistors have strange values, like 330 and 470 Ohms, instead of nice round numbers like 300 or 500 Ohms?

It turns out that standard resistor values form a preferred number series defined by the EIA. 5% values are part of a standard called E24. The standard is based on a geometric series - each value is approximately 1.1 times the previous one in the set.

EIA Resistor Values Explained [via The Steampunk Workshop]

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Comments

Oldest comments listed first.

Posted by: KNfLrPn on January 14, 2009 at 11:13 AM

It's true.

I remember when I figured this out. I was so proud of myself. And if you look at 1% resistors, it's the same thing but at a finer resolution.

If you think about it, there's no reason to have a higher resolution than the accuracy of the resistor.

Reply to this comment

Posted by: Metalworking on January 14, 2009 at 12:52 PM

Like linear dimensions with the "Renard numbers" : R5, R10, R20, and R40 ... or the rounded values...

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