[USMA:44059] Re: [SI] SI 10 question

[Stan Jakuba]

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" <j...@metricmethods.com>
To: <si...@listserv.ieee.org>
Sent: 09 Mar 14, Saturday 22:25
Subject: Re: [SI] SI 10 question


Paul,

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" <bbarr...@verizon.net>
To: <si...@listserv.ieee.org>
Sent: 14 March, 2009 20:19
Subject: Re: [SI] SI 10 question


Mr. 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" <jbfoo...@comcast.net>
To: "Bruce Barrow" <bbarr...@verizon.net>
Sent: Thursday, March 12, 2009 1:17 PM
Subject: FW: SI 10 question


Mr. 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 the SI 10
standard, I would have sent the request directly to you.

Lyle Bowman.

------ Forwarded Message
From: Lyle Bowman <jbfoo...@comcast.net>
Date: Tue, 10 Mar 2009 15:12:50 -0700
To: "James R. Frysinger" <j...@metricmethods.com>
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.1 of 
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
I
note that the BIPM SI Brochure also lists both of these. The ASTM Form 
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" <j...@metricmethods.com>
Date: Tue, 10 Mar 2009 16:02:43 -0500
To: Lyle Bowman <jbfoo...@comcast.net>
Cc: <d.rin...@ieee.org>, <j.frysin...@ieee.org>, <b.bar...@ieee.org>,
<m.kipn...@ieee.org>, <r.ge...@ieee.org>, <k.breitfel...@ieee.org>,
<y.hos...@ieee.org>
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 are
pleased to hear that you are working towards improved metrication of
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

d.rin...@ieee.org 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
d.rin...@ieee.org
****************************************************************

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 
(Section
3.5.1, item d)) says to leave a space between a 'numerical value and 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: jbfoo...@comcast.net

--
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