Support characters used in our field

Drawing Schematics, Hierarchical Design, BOM, Exporting net-lists, etc.
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bcsteeve
Posts: 28
Joined: 16 May 2015, 00:35

Re: Support characters used in our field

#11 Post by bcsteeve » 22 Jun 2015, 11:40

BS1852 is well named, because it is B.S. and is exactly the example I gave earlier why we need to be clear! Right from that wikipedia page, BS1852 tells us that R47 = 0.47 Ohms. Does it? So when I see a resistor on a schematic with R54 and R47 both beside the symbol, is it resistor #54 with a value of 0.47 Ohms or is it resistor #47 with a value of 0.54 ohms? Or it could be 47 or 54 Ohms and the person was either misunderstanding BS1852 or was using a home-brew. I mention that last possibility because that's EXACTLY what I came across just last month.

And having to write "470000nF" isn't really a solution either.

envisionelec
Posts: 18
Joined: 07 Apr 2015, 10:14
Location: Centerville, OH

Re: Support characters used in our field

#12 Post by envisionelec » 21 Apr 2016, 10:17

bcsteeve wrote:BS1852 is well named, because it is B.S. and is exactly the example I gave earlier why we need to be clear! Right from that wikipedia page, BS1852 tells us that R47 = 0.47 Ohms. Does it? So when I see a resistor on a schematic with R54 and R47 both beside the symbol, is it resistor #54 with a value of 0.47 Ohms or is it resistor #47 with a value of 0.54 ohms? Or it could be 47 or 54 Ohms and the person was either misunderstanding BS1852 or was using a home-brew. I mention that last possibility because that's EXACTLY what I came across just last month.

And having to write "470000nF" isn't really a solution either.

Don't be ridiculous. Wikipedia is incorrect - 0.47 ohms is 0R47 which is very clear.
Nanofarads is up to good debate. I prefer values between 1uF and 1000pF to be denoted in nF.
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bcsteeve
Posts: 28
Joined: 16 May 2015, 00:35

Re: Support characters used in our field

#13 Post by bcsteeve » 21 Apr 2016, 12:09

What is "ridiculous" is what you took from my point? Wikipedia's mistake is irrelevant. The point wasn't 0.47 vs 47, the point is we don't know if "R47" is an indication of its value or if it is the 47th resistor on the page.

MDman
Posts: 43
Joined: 26 Oct 2011, 02:53

Re: Support characters used in our field

#14 Post by MDman » 24 Apr 2016, 04:41

Well I don't know about you fellas, but when I do my values for parts I do it like this, 47R 3k 100k, 1M 0.1R, 100p 100n 100u.
Now if you were throwing some inductors among the mix, it would probably bee good not to be lazy and for capacitance values add the F, eg nF pF uF, just so when you put a 470uH inductor no one gets confused!

Why anyone would put the R in front of a resistance value is beyond me, when the letter is in front it is a refdes, eg R10(resistor 10), when the letter is at the end it is a value eg 47R(47 ohms).

bcsteeve
Posts: 28
Joined: 16 May 2015, 00:35

Re: Support characters used in our field

#15 Post by bcsteeve » 24 Apr 2016, 12:56

I agree that makes sense... but your personal convention is by no means a standard, unfortunately. MANY schematics (often from UK in my experience) denote values with a leading R.

Again... all becomes moot if the Ohm symbol were incorporated into the schematic.

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