×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Is there a standard symbol set?
2

Is there a standard symbol set?

Is there a standard symbol set?

(OP)
In the study of Engineering I am constantly plagued by the haphazard use of symbols. The latest offence was this (from my textbook which shall remain unidentified to protect the guilty wink)



My author has moved from using 'N' for Newtons to using it for rpm (arguably, for a Number of rpm) without pausing for breath.

Everyone will have seen this lack of consistency; everyone will have their favourite horror story. However, before we censure anyone for lack of discipline we have to establish whether the rules for such discipline exist. Therefore, my question is, "Is there an accepted standard set of individually distinctive symbols for engineering values? Since I haven't been able to find one, I am of the opinion that such does not exist (I would appreciate being corrected bow) so I have to add the question, "Is such a thing possible?

----------------------------------------
Artificial Intelligence is no match for Natural Stupidity

RE: Is there a standard symbol set?

Well, of course not. Have you considered how many quantities and constants there are? A VERY typical error in Mathcad is to define something like m=5kg and then use it in something like PE=mgh, and wind up with kg*J/m

So, there, m for mass, m for meter.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //www.engineering.com/AskForum/aff/32.aspx
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: Is there a standard symbol set?

Be happy you're not in the concrete industry. Their code uses symbols not even found in the thousands available through Microsoft.

RE: Is there a standard symbol set?

Even within Mathcad, there are anomalies. The SI symbol for gram is g, so kilogram is kg, etc. In Mathcad, g was assigned to the standard value of gravitational acceleration 9.80665, so gram becomes gm, while kilogram remains kg.

Nevertheless, you can look at http://physics.nist.gov/Pubs/SP330/sp330.pdf for standard accepted usage of units.
Or the CODATA Recommended values of physical constants: http://arxiv.org/pdf/1507.07956.pdf You can easily see conflicts, e for electron charge or for Euler's constant. F for the Faraday constant or for farad? R for the gas constant or for the Rankine?

Life used to be much simpler; there were fewer things that we knew, and most disciplines didn't interact with others. That's no longer the case.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //www.engineering.com/AskForum/aff/32.aspx
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: Is there a standard symbol set?

You're just confusing variables with units' symbols. There's no inconsistency (offence) here. Force, F (N). Rotational velocity N (rpm) or ω (rad/s).

Many people make problems for themselves by using unit names as variables. I often see "rpm" as a variable name (in computer programs and formulae). I've never seen "N" as a force variable though, and your author clearly doesn't use it either.

Steve

RE: Is there a standard symbol set?

Furthermore you can Google "ISO TR 25679 2005" and download free

RE: Is there a standard symbol set?

"My author has moved from using 'N' for Newtons to using it for rpm "

It looked to me italicized N was used for rpm, and non-italicized N for Newtons.

My recollection is lower case N (n) appears for rpm from time to time in some industries.
like this -
http://www.chiaravalli.com/pol/pdf_motori/SIMBOLI....

Yes, a reference table up front would seem to be good manners.

I find the use of acronyms by various industries has always been confusing, but nowadays has become far worse. Seems like if I'm not " in the club " I am not welcome.

RE: Is there a standard symbol set?

I too see no offence in using N for Newtons then N for angular velocity. In one case it is used as the universal SI symbol for the Newton, a unit of measure. In the other case it is use as a variable. These are two different purposes that pose no conflict in the same article.

Tunalover

RE: Is there a standard symbol set?

(OP)
Thanks to all who contributed to that discussion. thanks May I summarize -

Somptinguy and tunalover both picked up a point I think lies an the base of the issue:
Many people make problems for themselves by using unit names as variables. I often see "rpm" as a variable name (in computer programs and formulae). I've never seen "N" as a force variable though, ...

Tmoose also makes the valid point: ... a reference table up front would seem to be good manners.

Perhaps we will make things easier on ourselves by sticking to these simple concepts. reading

----------------------------------------
Artificial Intelligence is no match for Natural Stupidity

RE: Is there a standard symbol set?

Most good tech references I have seen include a table defining the meaning of each symbol used. But I can appreciate the problem described. I do design of aircraft gears, and two of the primary tech references I use are the MMPDS metallic materials handbook and AGMA gear standards. MMPDS uses lower case alpha for CTE, and AGMA uses lower case alpha for pressure angle.

RE: Is there a standard symbol set?

I sympathize with the OP's complaint. Often the hardest part of reading a technical book or report is figuring out what the symbols represent. In this example it would be very bad practice to use the same symbol for two different things in one equation. However, that is not the case here. One N is italicized, but that is not very obvious. On the author's computer the fonts were probably more different.
A similar problem happens in posts on this forum where someone answers a question with an equation without defining the symbols. We all have to remember that the purpose of writing is to communicate ideas, not to put squiggles onto a screen.

RE: Is there a standard symbol set?

It is convention is physical sciences that units (Newton, N for example) are distinct from variable or parameters (Turn Rate, N for example) and therefore can co-exist side by side.

RE: Is there a standard symbol set?

Units of measure like Newton, Volt, Kelvin, etc, that are based on a person's name are proper nouns, and should be capitalized.

RE: Is there a standard symbol set?

Actually, not.

Quote (NIST Special Publication 330 2008 Edition)

Unit names are normally printed in roman (upright) type, and they are treated like ordinary nouns. In English, the names of units start with a lower-case letter (even when the symbol for the unit begins with a capital letter), except at the beginning of a sentence or in capitalized material such as a title. In keeping with this rule, the correct spelling of the name of the unit with the symbol °C is “degree Celsius” (the unit degree begins with a lower-case d and the modifier Celsius begins with an upper-case C because it is a proper name).

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //www.engineering.com/AskForum/aff/32.aspx
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: Is there a standard symbol set?

@IRStuff
Am I crazy or is that conflicting?

First and Second sentences: "Unit names are normally printed in roman (upright) type, and they are treated like ordinary nouns. In English, the names of units start with a lower-case letter"
Third sentence: "In keeping with this rule, the correct spelling of the name of the unit with the symbol °C is “degree Celsius” (the unit degree begins with a lower-case d and the modifier Celsius begins with an upper-case C because it is a proper name)."

The third sentence would have us spell it Hz and Hertz. Per the second sentence, hertz would be Hz for the symbol and "hertz" in full. In fact, this trends with Kilohertz, and other multipliers, rather than KiloHertz.

I'm confused as to why the third sentence insists upon a capitalized Celsius, when referring to the unit, rather than the astronomer, then.

Edit-to-add: I suppose because "degree Celsius" is not a unit. "Degree" is a unit. "Celsius" is a 'modifier' per NIST, apparently. Nevermind - I should have thought it out more.

RE: Is there a standard symbol set?

No confusion; a newton-meter (N*m) is different than a nanometer (nm) per the SI usage guide. The two distinctions are the multiplication symbol between the newton and the meter, and the symbol for the newton is "N." THAT, at least, is pretty straightforward.

The degree-Celsius is unique in that it's the only SI unit that takes a proper name modifier, for apparently historical reasons, just like the base unit for mass is the kilogram, instead of the gram, for historical reasons.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //www.engineering.com/AskForum/aff/32.aspx
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers

RE: Is there a standard symbol set?

So per NIST spelt out they don't get abbreviated but when used as letter symbol it would appear the ones nominally named after people are capitals as opposed to lower case.

Which is what I thought we were talking about but now realize you were more specifically responding to tbuelna.

http://physics.nist.gov/cuu/pdf/sp811.pdf

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Is there a standard symbol set?

One problem is that different people's minds work differently, and what seems logical to me may not to you.

I would prefer that in any given section of a work, that all variables are defined in that section. However, the concrete codes have tried to define variables that are valid for the entire code. This means that numerous variables are Greek letters with multi-letter subscripts, which make them a pain to type, and also irritating to have to flip back 200 pages to find the definition.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources