[gta02-core] Values and units in schematics

Rene Harder rehar at saweb.de
Wed Jul 1 06:02:48 CEST 2009

Werner Almesberger wrote:
> Sure, but 1200U isn't all that uncommon. I even Digi-Key use
> only increments of six orders of magnitude for things as basic
> as capacitors. Not that I particularly enjoy looking up 100 nF
> capacitors there - "10000pF" has an awful lot of zeroes ...

Yes for values of the physical components this style is widely used at
least for ceramic caps, but here we need to differentiate, we are
talking about the schematics and not about the physical cap.

IIRC 10000pF is indeed quite uncommon mostly 0.01uF is used for 10nF. ;-)

> Hmm, maybe it's just me, but I noticed that 10 nF/10 uF left me
> with a doubt if I had seen the prefix properly. It's not an issue
> of not being able to read it, but one of seeing what one expects
> to see when giving it a quick glance.
> But perhaps it's not so bad in the end ... your schematics with
> lower-case units certainly are readable enough.
> So ... "simple components" (resistors, capacitors, and inductors):
> - one mixed-case letter per value, serving as decimal point,
> - where that letter is a unit, no space between number and unit,
> - secondary attributes like tolerance (1%), material (X5R), or even
>   ESR (50 mOhm - there we have it ! :), don't make this a complex
>   components.
> Complex, multi-valued units:
> - use regular SI notation (5.6Vac), except
> - no space between value and unit
> How does this sound ?

Yeah that sounds perfect, I'm wondering what the other people think, so
far nobody mentioned anything, did they?

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