It's good to have newcomers in a field which has so many "that's just
how it's always been" methods and means.

New blood helps us look at ourselves critically.

In the case of resistors, there are several considerations:
 * Machine vision systems can significantly more easily ID color coded
resistors than numbers
 * It's much easier to print - if you want numbers on a round resistor
you have to print them several times around the cylinder or else they
can't be seen as readily.
 * Color bands are much larger and therefore easier to read - imagine
printing numbers on the resistor itself - they're going to be tiny,
and being on a curved surface they won't be as simple to read and see
as color bands.
 * "This is the way it's always been done" is a valid ongoing reason -
it works, and changing over would introduce a huge cost to
manufacturing (which would pass down to us), not to mention how
they're used (machine vision checking, etc)
 * We're moving more towards another package (SMT) entirely anyway, so
why revamp a system that it slowly going away?

Regarding printing resistor values with less cryptic numbers:
 * There's simply not enough room to make it legible.
 * You need more digits to specify your system (6834 vs 9.76M, and
unless you give the decimal a full digit's worth of space it's hard to
identify)
 * Your example of 10e9 is great - but if you're always going to have
the e, then why not simply remove it and mark the capacitor 109?
 * Further, what is the base unit, and how do you specify values
smaller than the base unit without adding more characters?

In this case, I believe you'll just have to live with the decisions
others made in this industry years ago.  As you can see, most of the
engineers on this list largely agree with how the system works now,
but please do bring up other issues as you learn.

It's always good to revisit past decisions, even if they arent' going
to change - they may positively affect current decisions.

-Adam

On 6/24/08, Tom=E1s =D3 h=C9ilidhe <toe@lavabit.com> wrote:
>
>
> Adam Field wrote:
> > It's not a  "color game". There are many reasons why the color code
> > exists. The primary being that when it was introduced, it was easier
> > to band resistors than to try and print numbers on them. The second
> > that comes to mind is that the resistor can be placed at any angle and
> > still have its value readable.
> >
>
> Really? I thought it was brought in to ostracise colour-blind people.
>
> You say they can be read from any angle, but I bet you I can read "220
> ohms" backwards and upside down handier than I can read a colour-band.
>
> > Once you learn it, it becomes very easy to distinguish values from
> > each other. Especially when you have a pile of them on your workbench.
>
> Ah yes I've known the colours off by heart for a few years now, I
> instinctively look for a "red red brown" when I'm playing around with
> LED's. Despite that, I still think they're absolutely stupid in this day
> and age, especially since they unfairly discriminate against
> colour-blind people.
>
> I can't think of anything more intuitive than having "220 ohms" printed
> on a resistor.
>
> I had a capacitor one time that had "10e9" printed on it; I went to the
> wall chart to see what it was, and to my delight it was 10 nanofarrads.
> I was actually surprised that the manufacturer actually showed some cop o=
n.
>
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