# [reproduced] standard resistor form and instructions

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Time just to work, I remember one time to develop a product, BOM has a resistance of 500 I used resistance. Later I have no procurement told resistance 500, only 510, then wonder why resistance so integer no? Then only some resistance, but the resistance value of the resistance value is not what is still a little confused. Recently, not many things, spend a little time on the issue.

The United States of America Electronic Industries Association defines a standard resistor value system, this system is defined in the last century, when the resistance is carbon membrane process, the accuracy is very low. In order to understand the resistance value system, resistance with precision of 10%, if the first resistance value is 100, there is no need to do 105, because the resistance of 100 precision is 90 to 110, so the second significant resistance value is 120 resistance accuracy, range from 110 to 130Ω. In this way analogy from 100 to 1000 resistance value is 100, 120, 150, 180, 220, 270, 330 and so on, this is the resistance of the E12 series of EIA defined value. One might ask why not like 100, 120, 140, 160, 180, 200 of this? In fact the resistance value is in accordance with the following formula calculated, n said the n values, N category in the EIA definition( N=192, 96, 48, 24, 12, 6, 3). If you want to ask me why such a formula? This formula will know more profound, I can not answer.

EIA defines a few series resistance values, are E3 E6 E12 E24 E48 E96 E192, digital E back from 100 to 1000 a total of several other resistance, resistance is obtained according to the index of multiplication and division of 10, such as 4.7, 4.7K etc.. All precision defines series and value as follows: E3 (50% accuracy is no longer in use) E6 20% E12 10% E24 5% precision accuracy of precision of E48 2% E96 1% precision accuracy

E192 0.5%, 0.25%, 0.1% and higher accuracy

The next page can be seen in the table, we choose resistance when, should try to use compatible with low precision series, such as E6, E12 and so on, so you can easily purchase, low price, short delivery cycle. Compatible with low accuracy is not to say that we must use 10% or 20% precision, you can choose 1%, accuracy of 5%, but the best from E6, E12 series of some resistance to choose. If you don't want to trouble you can click the online calculation in the table, as long as the input of the expected value and the resistance to which precision series can automatically calculate the standard resistance you want value.

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Posted by Rick at November 16, 2013 - 4:37 AM