[gta02-core] Values and units in schematics

Rene Harder rehar at saweb.de
Wed Jul 1 02:17:19 CEST 2009

Werner Almesberger wrote:
> Rene Harder wrote:
>> Well, but we might have millihenry somewhere in the schematics and then
>> we use M=Mega for resistors and M=milli for inductors?
> We could just avoid "milli" and use 1200U for the 1.2 mH inductor.
> For small resistances, since it's the low end, maybe 0R02 for
> 20 mOhm. Not pretty, but reasonably unambiguous.

or we could use 0R+j4R7 @100Hz for an inductor (ideal)  :-D
Does it makes sense to use such a cryptic term and how about readability

The problem with using uncommon notations is that you need to study the
definitions first before you can read the schematics, I believe that's
one reason why there are only a few common convention for electrical
schematics. If you now break them or introduce an obvious conflict,
that's not good for potential reviewers because they might get confused
and need more time to get into it.

If I open a schematic see a resistor labeled 1M2, i don't have any
doubts that this will be an 1.2*10^6 Ohm resistor, but then i see an
inductor labeled with 1M2 and I start wondering. Sure in the end, I'll
assume that this is an 1.2*10^-3 Henry inductance and the resistor is in
the mega Ohm range but still there will be some doubts.

So why exactly do we should to go for it?
You said it will improve readability, does it really increase readability?
I never had any problems with seeing the difference between 1n2 and 1u2
as far as i still could read the numbers  and believe me I've seen quite
a few schematics. What i had big problem with were unclear values,
units, labels, random wire paths or just inconstancy because they cost
me time and time was money for me those days  ;-) . Fortunately that
didn't happen very often just every now and then.

If you really think readability is a problem we might want to increase
the font size instead.

Anyway, that's just my opinion but we need to move on and make a
decision before we get stuck here forever.

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