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Science Forum Index » Electronics - Basics Forum » resistor nomenclature...
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 Posted: Mon Jul 14, 2008 11:56 am |
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| Posted: Mon Jul 14, 2008 12:25 pm |
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On Jul 14, 3:08 pm, John Fields <jfie... at (no spam) austininstruments.com> wrote:
Ah.
http://www.redcircuits.com/Page2.htm
I thought Resistor 18 was a 22 ohm.
Is it 0.22 ohm?
Michael |
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| John Fields... |
| Posted: Mon Jul 14, 2008 5:08 pm |
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On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett at (no spam) gmail.com wrote:
Quote: http://en.wikibooks.org/wiki/Practical_Electronics/Resistors
So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
Atlantic)
---
I think it needs a zero in front of it, like 0R2
JF |
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| christofire... |
| Posted: Mon Jul 14, 2008 5:54 pm |
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"John Fields" <jfields at (no spam) austininstruments.com> wrote in message
news:ugjn7454bj03ii1m975o9eni73ubdpvele at (no spam) 4ax.com...
.... and not everyone 'east of the Atlantic' uses a comma for a decimal
point. How crass!
C |
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| Eeyore... |
| Posted: Mon Jul 14, 2008 9:49 pm |
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mrdarrett at (no spam) gmail.com wrote:
Quote: http://en.wikibooks.org/wiki/Practical_Electronics/Resistors
So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
Atlantic)
I'd write it 0R2 myself. Unless it's simply a component reference
designator like R17 which is what it appears to be on that page.
Graham |
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| Peter Bennett... |
| Posted: Mon Jul 14, 2008 9:52 pm |
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On Mon, 14 Jul 2008 15:25:04 -0700 (PDT), mrdarrett at (no spam) gmail.com wrote:
I would assume that R18 is 0.22 ohms, based on the general format of
the parts list.
I would much prefer to see the value written as 0R22, so it can't be
confused with R22, the twenty-second resistor in the circuit.
--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca |
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| John Larkin... |
| Posted: Mon Jul 14, 2008 10:42 pm |
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On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett at (no spam) gmail.com wrote:
Quote: http://en.wikibooks.org/wiki/Practical_Electronics/Resistors
So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
Atlantic)
Michael
Horrible circuit, horrible nomenclature.
The right way to write 0.2 ohms is "0.2" or "0.2R", if you can't make
the omega symbol.
John |
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| ... |
| Posted: Tue Jul 15, 2008 1:49 pm |
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On Jul 15, 3:04 pm, Eeyore <rabbitsfriendsandrelati... at (no spam) hotmail.com>
wrote:
Quote: mrdarr... at (no spam) gmail.com wrote:
So you spec 2E-1 for your 0.2 ohm resistors?
Believe it or not, that style was briefly once used.
Graham
What's wrong with that style? I kinda like it - lots more than R2 or
0R2.
Michael |
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| Eeyore... |
| Posted: Tue Jul 15, 2008 5:04 pm |
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mrdarrett at (no spam) gmail.com wrote:
Quote: So you spec 2E-1 for your 0.2 ohm resistors?
Believe it or not, that style was briefly once used.
Graham |
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| John Fields... |
| Posted: Tue Jul 15, 2008 5:24 pm |
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On Tue, 15 Jul 2008 23:04:24 +0100, Eeyore
<rabbitsfriendsandrelations at (no spam) hotmail.com> wrote:
Quote:
mrdarrett at (no spam) gmail.com wrote:
So you spec 2E-1 for your 0.2 ohm resistors?
Believe it or not, that style was briefly once used.
---
Hell, I use it all the time on LTspice schematics.
JF |
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| John Larkin... |
| Posted: Tue Jul 15, 2008 7:04 pm |
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On Tue, 15 Jul 2008 17:12:22 +0100, Eeyore
<rabbitsfriendsandrelations at (no spam) hotmail.com> wrote:
Quote: Decimal points have no place on schematics.
Grahgam
So how do you express 33.25 MHz? 95.2 nanoseconds? Turns ratio of
2.5:1?
33MHz25
95ns2
2T5:1
but if decimal points slide off the page, I suppose colons do, too.
And of course, comments and notes can't have periods.
John |
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| Michael A. Terrell... |
| Posted: Tue Jul 15, 2008 7:37 pm |
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John Larkin wrote:
Quote:
And of course, comments and notes can't have periods.
No, but Donkeys do, and quite often.
--
http://improve-usenet.org/index.html
If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm
Sporadic E is the Earth's aluminum foil beanie for the 'global warming'
sheep. |
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| Ross Herbert... |
| Posted: Tue Jul 15, 2008 9:48 pm |
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On Tue, 15 Jul 2008 06:47:48 -0700, John Larkin
<jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
:On Tue, 15 Jul 2008 10:06:47 GMT, Ross Herbert
:<rherber1 at (no spam) bigpond.net.au> wrote:
:
:>On Mon, 14 Jul 2008 20:42:51 -0700, John Larkin
:><jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
:>
:>:On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett at (no spam) gmail.com wrote:
:>:
:>:>http://en.wikibooks.org/wiki/Practical_Electronics/Resistors
:>:>
:>:>So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
:>:>Atlantic)
:>:>
:>:>Michael
:>:
:>:Horrible circuit, horrible nomenclature.
:>:
:>:The right way to write 0.2 ohms is "0.2" or "0.2R", if you can't make
:>:the omega symbol.
:>:
:>:John
:>
:>
:>I don't agree John 
:>
:>If you can't make the Omega symbol you either use "0.2 ohms" or "0R2" where
the
:>R replaces the decimal point.
:
:I do not. I use correct scientific notation, and correct engineering
:units, not some weird amateur audio thing.
:
:John
:
So, if your documentation specifies say a "0.2R" resistor and the decimal point
goes missing in printing, the result is then "0 2R". How can you claim that this
is not ambiguous? You need to get with the times John. I can say this with
impunity because I am 68 and have been working in electronics since the mid 50's
and a new idea which makes written resistor values non-ambiguous seems wise to
me. |
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| John Larkin... |
| Posted: Tue Jul 15, 2008 10:43 pm |
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On Wed, 16 Jul 2008 02:48:35 GMT, Ross Herbert
<rherber1 at (no spam) bigpond.net.au> wrote:
Quote: On Tue, 15 Jul 2008 06:47:48 -0700, John Larkin
jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
:On Tue, 15 Jul 2008 10:06:47 GMT, Ross Herbert
:<rherber1 at (no spam) bigpond.net.au> wrote:
:
:>On Mon, 14 Jul 2008 20:42:51 -0700, John Larkin
:><jjlarkin at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
:
:>:On Mon, 14 Jul 2008 14:56:03 -0700 (PDT), mrdarrett at (no spam) gmail.com wrote:
:>:
:>:>http://en.wikibooks.org/wiki/Practical_Electronics/Resistors
:>:
:>:>So does R2 mean 0.2 ohms? (0,2 ohms for those of you east of the
:>:>Atlantic)
:>:
:>:>Michael
:>:
:>:Horrible circuit, horrible nomenclature.
:>:
:>:The right way to write 0.2 ohms is "0.2" or "0.2R", if you can't make
:>:the omega symbol.
:>:
:>:John
:
:
:>I don't agree John
:
:>If you can't make the Omega symbol you either use "0.2 ohms" or "0R2" where
the
:>R replaces the decimal point.
:
:I do not. I use correct scientific notation, and correct engineering
:units, not some weird amateur audio thing.
:
:John
:
So, if your documentation specifies say a "0.2R" resistor and the decimal point
goes missing in printing, the result is then "0 2R". How can you claim that this
is not ambiguous?
How about if the "2" goes missing? Then what do you do?
Quote: You need to get with the times John.
Get with the times? I use a CAD program that doesn't lose characters.
And a B-size laser printer that prints like pages from Sunset
magazine. Our digital copier is so good that the only way you can tell
the copies from the original is that they're warmer; it even feeds,
collates, and staples the copy, or emails you a PDF of the original.
But we seldom copy schematics; the printers and the copiers are
networked, so it's easier to just spool another one from the library
server, finish your latte, then go pick it up.
Are you still drawing schematics on butcher paper with dull pencils,
and copying them on the fly-spec'd machine at the supermarket? Or
exposing blueprints in sunlight?
I can say this with
Quote: impunity because I am 68 and have been working in electronics since the mid 50's
and a new idea which makes written resistor values non-ambiguous seems wise to
me.
One of the first things they taught us in engineering school was to
make clear decimal points. It's surprising how many people can't
master the technique.
But the real issue is that, in a professional outfit, a schematic is a
reference drawing, and does not control configuration. What does
control configuration is an assembly drawing and a bill of materials.
And the BOM doesn't call out resistors by value, it calls them out by
stock number. Since it's common for an ECO to change a BOM, or to have
several dash-numbered versions of one pcb assembly, each with its own
BOM, the schematic can't be relied on to call out the actual
resistance, if R112 is indeed installed at all. Production doesn't
pull a 4.99K 0805 1% resistor; they pull stock number 302-3761.
John |
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| whit3rd... |
| Posted: Wed Jul 16, 2008 10:49 am |
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On Jul 16, 7:08 am, John Larkin
<jjlar... at (no spam) highNOTlandTHIStechnologyPART.com> wrote:
Quote:
The "standard" is SI units and nomenclature. The "no decimal points"
mess is an amateur affectation. My customers are scientists and
aerospace engineers; they would think I'd gone senile if I started
putting 0R118 next to R118.
But, R118 is a NAME that has to be looked up in an
associated table to find out what it refers to. 0R118 is
a VALUE (and an odd one, who uses 0.118 ohm
resistors - the number of digits suggests a sub-1%
part).
In 'R118' the R designates a resistor. In '0R118', it
designates a radix point.
When time comes to look inside my thermostat, the little
glued-into-the-lid schematic would be more useful if
it has a blurry '0R118' next to a resistor symbol than
if it tries to fit in a full specification (size, fire rating,
value, tolerance, etc). Certainly the lid of the thermostat
doesn't have room for a tabulated parts list.
There's a place for clear engineering documents, and
a place for slapdash notations glued inside access
panels. Both are useful. If the lack of standards is
bothersome, let's write one up. RFC-0R118, perhaps? |
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