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 three
quantities correctly. The units cause no confusion. Contrary to your
statement they
eliminate it. The fact that one needs to be knowledgeable about units and SI
applies 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 than
other 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 the
examples with it. They should help. At the next revision, I ought to include
Pierre'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 Hz
1 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 question
Stan,
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 do
not 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 question
If you prefer, Stan, please read my 8600/s as 8600 s-1. It seems both of
us 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
anything
else! Of course, you can SAY whatever you want, but the subject here is
the
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 such
education is provided at the high-school level. But perhaps only in the
metric 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 question
You 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 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"
<[email protected]>
To: <[email protected]>
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"
<[email protected]>
To: "Bruce Barrow" <[email protected]>
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 <[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.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" <[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 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
[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
(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: [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
