Throwback Thursday: Electronic Components with Odd Values

Last year around this time, Brandon took a look at electronic components and answered the question many of us have asked: “Why do electronic components have such strange values?” As Brandon himself says, “If you’ve been around electronics for a while, you’ve probably noticed that components like resistors, capacitors, zener diodes, and inductors come in some odd values. Looking at the chart below, there seems to be no clear rationale behind the values, but there is a pattern. 47kΩ resistors and 22μF capacitors are everywhere, but not 40kΩ or 50kΩ resistors, or 20μF or 30μF capacitors. So what’s the deal? It all has to do with preferred numbers.”

Charles Renard introduced a system designed so that components have a minimum and maximum values that overlap, so that any electronics needs can be met by at least one part. While there have been modifications since then, we still use a system based on that one.

E12_series_tolerance.svg
This graph shows how any value between 1 and 10 is within ±10% of an E12 series value, and its difference from the ideal value in a geometric sequence. By Anders Andersson from Wikimedia Commons.

Brandon has plenty more details and in-depth history in his blog post to help you make sense of an otherwise confusing topic. Check it out, and let us know what sort of things you’d like to see in a future throwback post.

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About Amber Mear

I was the Digilent blog editor, and now I'm a contributor. I love learning about wearables and writing about social issues in STEM. Outside of work, I can be found watching Netflix with my cat, working on an art project, or trying to find new, delicious local foods.

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2 Comments on “Throwback Thursday: Electronic Components with Odd Values”

  1. Component selection is a process of selecting a suitable component or a set of similar components from different suppliers for the designed circuit to perform its intended operation.

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