Stan,
I admire your tenacity and your style of boiling things down to simplest principles. But I must say that I do not entirely agree with you on a point or two.
I most certainly **cannot** agree on this statement of yours:"Writing 8600/s violates the SI rule for writing a number with a unit. It is also against common sense."
Please look at section 5 of the SI Brochure. Specifically, look at section 5.3.3. The first statement at first would seem to support your point of view; it says that a space always intervenes between number and unit. But the second statement provides the rationale for that; that rationale is that the space stands for a multiplication sign. Essentially, the CIPM/BIPM forgot to consider a derived unit with nothing in the numerator, that is with all the units making it up in the denominator as in the case of reciprocal seconds.
In the case of "8600 per second", we have a case where the number is divided by the unit, not multiplied by the unit. (The two operators are inverse, one represented by a space and one by a solidus.) So in the construction 8600/s, the solidus (/) stands for the division sign. You yourself provide a beautiful example of this and it is one that the SI Brochure itself uses: 1/s. Here we have the number 1 divided by the second. By extension, therefore, using the rules of the quantity calculus and simple algebra, we can write 8600/s.
The point is that we should not run the number up against the unit. In 452 s a space intervenes to indicate multiplication. In 8600/s a solidus intervenes to indicate division. The numerical value and the unit do not abut each other in either example. The quantity calculus is happy.
You need not take my word alone for this. Please look at NIST SP 811, section 7.5. Three of the five examples of correct writing provided there are:
the sensitivity for NO3 molecules is 5 x 10^10/cm^3
the neutron emission rate is 5 x 10^10/s
the number density of O2 atoms is 3 x 10^18/cm^3
I do wonder, though, if that was not meant to be N2O3 or NO2 instead of NO3.
On a minor point, I'm not sure what your concern is about "m · s-1" in
SI 10, except that you think there are spaces on either side of the
center dot (multiplication dot). Perhaps you think the typesetter used
spaces there and I think the typesetter just used leading to allow the
center dot to be viewed more clearly. At the moment, I see in SI 10
clause 2.1.2 that the unit for "speed, velocity (meter per second) has
been represented as m/s. The only instance I can find of your example is
in 3.5.3.2. It looks fine to me and I don't see any intentional spaces
surrounding the center dot, just generous leading similar to all the
other such examples in SI 10. On this point, I feel like we're done to
styling the leg hairs on a gnat. Space is in the eye of the reader, I
suppose. And leading is in the hand of the typesetter.
Jim Stan Jakuba wrote:
Jim:Not sure what you mean -- to agree on seeing one thing more often than another one?I think that we agree on this: Writing 8600/s violates the SI rule for writing a number with a unit. It is also against common sense. The three paragraphs in "FREQUENCY" show the SI unit for each of the threequantities correctly. The units cause no confusion. Contrary to your statement they eliminate it. The fact that one needs to be knowledgeable about units and SIapplies here the same as for any other discipline. The expression m/s is SI. SI allows other forms, starting with the BIPM brochure's m·s-1 interpreted in SI10 incorrectly as m · s-1 (the -1 is an exponent in both cases). Whether one sees one form more frequently thanother is irrelevant. When options exist, the usage is likely different among professions and regions.I am attaching the chapter from my book again, this time including all theexamples with it. They should help. At the next revision, I ought to includePierre's becquerel thus having in it four units. FREQUENCY There are three kinds of frequencies, and correspondingly three different units: -- Angular Frequency, commonly called angular velocity. Its unit is rad/s. -- Cycle Frequency. It is defined as the number of periodic events (cycles) per second. This unit was given the name hertz (in honor of the German scientist), symbol Hz. -- Rotational Frequency, commonly called speed of rotation or simply speed. Its unit is s-1 (-1 is exponent) optionally written also as 1/s. Note: The units of the cycle frequency and rotational frequency are sometimes, and incorrectly, written as c/s or cps, and r/s or rps, respectively. These symbols could be misunderstood in non-English speaking countries. Furthermore, cycles and revolutions are not (SI) units; if used, these words should be spelled out or clearly abbreviated such as rev./s, rev./min. etc. in the respective language. ________________________________________________________________________ A Feel For Sizes 60 Hz: line frequency 530 Hz to 1600 kHz: AM radio 88 Hz to 108 MHz: FM radio ________________________________________________________________________ Equivalent Common Values 1 cps is 1 Hz1 rev./sec. is 1 s-1 (font problem -- -1 should be exponent) 1 rev./sec. is 2p rad/s (font problem -- p should be PI()).________________________________________________________________________----- Original Message ----- From: "James R. Frysinger" <[email protected]>To: "U.S. Metric Association" <[email protected]> Sent: 09 Mar 23, Monday 09:52 Subject: [USMA:44078] Re: SI 10 questionStan, I agree that in technical writing one will see the likes of 8600 s-1 and not 8600/s. In fact, in technical writing that I encounter, I see values of the form 4 m s-1 much more often than 4 m/s. At least we can agree on that much, I think. Jim Stan Jakuba wrote:Jim:I prefer not to read, or see, such a nonsense as 8600/s at all. And "I donot understand your form" not only because it is not SI but also because I have never seen it anywhere except perhaps in a poorly executed schoolwork assignment. Stan ----- Original Message ----- From: "James R. Frysinger" <[email protected]> To: "U.S. Metric Association" <[email protected]> Cc: "U.S. Metric Association" <[email protected]> Sent: 09 Mar 22, Sunday 21:41 Subject: [USMA:44069] Re: SI 10 questionIf you prefer, Stan, please read my 8600/s as 8600 s-1. It seems both ofus understand each form. I of course accept the latter as being quite valid. Jim Stan Jakuba wrote:You must be joking, Jim. Who would ever write 8600/s? In SI or in anythingelse! Of course, you can SAY whatever you want, but the subject here isthe WRITTEN language of SI symbols. It has been the common practice in technical literature for decades (including in the US, UK, and similar) to write 8600 s^-1 or 8600 min^-1, to use your number. If you had read the three paragraphs carefully (you had seen them many times before) you'd see that, contrary to what you say, those units make confusion impossible. Yes, to understand them, a bit of education helps but sucheducation is provided at the high-school level. But perhaps only in themetric countries. Stan Jakuba ----- Original Message ----- From: "James R. Frysinger" <[email protected]> To: "U.S. Metric Association" <[email protected]> Sent: 09 Mar 22, Sunday 14:47 Subject: [USMA:44061] Re: SI 10 questionYou may wish to consult Section 8.1 of NIST SP 811. One has to be careful with using 1/s (or s-1) for rotational rates. There is potential confusion whether one means shaft rotations per second or angular velocities of radians per second. So if I say, "The motor is running at 8600/s" what do I mean? Better to say, "The motor is running at a shaft rotation rate of 8600/s" or "The motor is running at an angular velocity of 8600 rad/s", whichever is the case. Of course those differ by a factor of 2 pi. Jim Stan Jakuba wrote:FREQUENCY There are three kinds of frequencies, and correspondingly three different units: -- Angular Frequency, commonly called angular velocity. Its unit is rad/s. -- Cycle Frequency. It is defined as the number of periodic events (cycles) per second. This unit was given the name hertz (in honor of the German scientist), symbol Hz. -- Rotational Frequency, commonly called speed of rotation or simply speed. Its unit is s-1 optionally written also as 1/s. Note: The units of the cycle frequency and rotational frequency are sometimes, and incorrectly, written as c/s or cps, and r/s or rps, respectively. These symbols could be misunderstood in non-English speaking countries. Furthermore, cycles and revolutions are not units; if used, these words should be spelled out or clearly abbreviated such as rev./s, rev./min., etc. Stan Jakuba ----- Original Message ----- From: "James R. Frysinger" <[email protected]> To: <[email protected]> Sent: 09 Mar 14, Saturday 22:25 Subject: Re: [SI] SI 10 questionPaul, Rotational speeds are usually given as revolutions per second or revolutions per minute. To that point, one would want to list both r/s and r/min. Some folks use Hz instead of r/s, especially for shaft rotational rates since that is a periodic function (angular position as a function of time). In my physics classes I required my students to use r/min rather than rpm. Jim Paul Trusten wrote:Bruce, this is revolutionary! (grin). I never thought of symbolizing that, and it should be symbolized, since we avoid KPH in favor of the correct km/h. Would it be more elegant, to use the base unit of time, and make the quantity revolutions per second, proposed symbol r/s? That would make, let's say, 5000 r/min change to about 80 r/s. I think perhaps not, since r/min is an established unit. Paul ----- Original Message ----- From: "Bruce Barrow" <[email protected]> To: <[email protected]> Sent: 14 March, 2009 20:19 Subject: Re: [SI] SI 10 questionMr. Bowman, You are coming up with some very good questions! Our IEEE Std on Unit Symbols, Std 260.1-2004, lists r/min as the appropriate unit symbol, and includes as a note, "Although use of rpm as an abbreviation is common, it should not be used as a symbol." I'm not sure ordinary mortals, as opposed to members of selected standards committees, understand the difference. I am proposing that our revised SI10 include only "r/min". Bruce ----- Original Message ----- From: "Lyle Bowman" <[email protected]> To: "Bruce Barrow" <[email protected]> Sent: Thursday, March 12, 2009 1:17 PM Subject: FW: SI 10 questionMr. Barrow, Jim may have forwarded my question re 'rpm' (shown below) to you already.Had I known you were the person more directly responsible for theSI 10 standard, I would have sent the request directly to you. Lyle Bowman. ------ Forwarded Message From: Lyle Bowman <[email protected]> Date: Tue, 10 Mar 2009 15:12:50 -0700 To: "James R. Frysinger" <[email protected]> Conversation: SI 10 question Subject: FW: SI 10 question Jim, Thanks for the prompt response to my question.Perhaps, you can help me with another question also. In Table A.1of the SI 10 standard (Page 36), the 'to convert from' column lists 'revolutions per minute (rpm)'. The previous E 380 standard listed both rpm and r/min, and Inote that the BIPM SI Brochure also lists both of these. The ASTMForm and Style for ASTM Standards document lists just r/min. Since the SI 10 has been my 'bible' for revising the some 35 ASTM standards I'm responsible for, I've used 'rpm' in those revisions. My question is why does the SI 10 standard list only 'rpm'? I've conjectured that 'rpm' was preferred because it definitely would not be mistaken for a SI unit, but 'r/min' might possibly be. Regards, Lyle. ------ Forwarded Message From: "James R. Frysinger" <[email protected]> Date: Tue, 10 Mar 2009 16:02:43 -0500 To: Lyle Bowman <[email protected]> Cc: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]> Subject: Re: SI 10 question Dear Mr. Bowman, I am the chair of a committee, some members of which represent the IEEE portion of the IEEE/ASTM Joint Committee for Maintaining SI 10. Your message has been forwarded to me for a reply. Standard practice in the U.S. is to use a space instead of a hyphen when unit symbols are used, whether the expression is in noun ("a width of 35 mm") or adjectival form ("35 mm film"). That would comply with the normative statements of IEEE/ASTM SI 10 as well as NIST SP 811. Further, and importantly, it complies with Section 5.3.3 of the SI Brochure (8th ed.) Your suggestion to make an explicit statement in SI 10 regarding application of this practice to the adjectival form is noted and will be considered for the revision (update) now in progress. Thank you for that thought! You may have noticed that SP 811 says the hyphen "is acceptable" (but not required) in adjectival forms when the unit name is spelled out ("35-millimeter film"). Personally, I prefer using a space there as well; the movement in language is generally toward economy of punctuation, except as needed to avoid ambiguity. Thank you very much for your interest in SI 10. Most certainly, we arepleased to hear that you are working towards improved metricationof ASTM standards. If you have any other questions, please do not hesitate to write or call. regards, James R. Frysinger (Jim) Chair, Standards Coordinating Committee 14 IEEE Standards Association [email protected] wrote:Jim, Please see the communication (below), regarding SI 10. Thanks,****************************************************************David L. Ringle Manager - IEEE-SA Governance, Policy & Procedures IEEE Standards Activities Department 445 Hoes Lane Piscataway, NJ 08854-4141 USA TEL: +1 732 562 3806 FAX: +1 732 875 0524 [email protected]****************************************************************March 4, 2009 I'm an ASTM member and have been given the task of revising the measurement units in many ASTM standards to SI units. The IEEE/ASTM SI 10-2002 standard has been my primary reference in doing this task. There's one question that I haven't been able to resolve, and that is whether to place a hyphen between a number and an SI unit when the combination is used in an adjectival sense. My SI 10 reference (Section3.5.1, item d)) says to leave a space between a 'numerical valueand a unit symbol', and does not comment on the possible adjectival usage. An earlier ASTM E 380 SI Standard says to hyphenate when the combination is used in an adjectival sense, and the current NIST Special Publication 811 (SP 811) says specifically not to hyphenate in that situation. Assuming that it's also the intention of the IEEE/ASTM 10-2002 standard to not hyphenate when a combination of a numerical value and a unit symbol is used in an adjectival sense, I'd recommend that a specific statement to that effect be included in the standard. I'd appreciate being informed if my above assumption is incorrect. Sincerely, Lyle Bowman 728 Montecillo Road San Rafael, CA 96904-3136 Phone: 415-479-3004 Email: [email protected]-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108 ------ End of Forwarded Message ------ End of Forwarded Message-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
-- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
