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'mF'
1999\11\03@060208 by Russell McMahon

picon face
>I've not yet EVER seen milliFarads.
>BillW

Which is an EXCELLENT reason to use correct prefixes - ie so that when you
DO meet milliFarads you know what mF means.

Electronics Australia magazine use mF for laaaarge filter capacitors in some
circuits - 10,000 microFarad on up and I have seen it used in a few other
places but can't think where at present. I personally would never use mF if
only because it is so rare that it invites disaster.

While we're on the correctness kick - ALL SI units MUST be in multiples or
sub multiples of 10^3.
ie horrendous measures such as cm are forbidden.

Angstrom is similarly almost forbidden except that, as it does not imply its
multiplier (or its major unit) in its name it is not liable to confuse.
However, use of centimetre will bring disaster on one's head sooner or
later.





     Russell McMahon
_____________________________

>From another world - http://www.easttimor.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))

1999\11\03@094135 by Nick Taylor

picon face
Russell,
Do you have a reference for 10^1 and 10^2 units being forbidden?  I
have the NIST Special Pub 811 (US) booklet in front of me and cannot
find any such reference.

Here is the list of terms that are "unacceptable":
erg, dyne, poise, stokes, gauss, oersted, maxwell, stilb, phot, fermi,
metric carat, torr, standard atmosphere, kilogram force, micron,
calorie,
x unit, stere, gamma, gamma (mass), gamma (volume).

These are "temporarily accepted for use":
nautical mile, knot, angstrom, are, hectare, barn, bar, gal, curie,
roentgen, rad, rem.

How many of you know how many yoctoFarads there are in one yottaFarad?

- Nick -

Russell McMahon wrote:
{Quote hidden}

1999\11\03@095326 by Sean Breheny

face picon face
This seems silly. How can you not allow gauss,erg,dyne,torr, and micron?
These are all in common use. More importantly, I think a bar is a dyne per
cm^2,so it would be really silly to allow a until but not the base units it
came from!

Sean

At 06:38 AM 11/3/99 -0800, you wrote:
{Quote hidden}

| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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1999\11\03@102543 by Tommy Bostrom

flavicon
face
I think the old saying applies
The metric system is conquering U.S. inch by inch
{Quote hidden}

1999\11\03@103814 by Nick Taylor

picon face
Sean,
That's the point of the SI units; to get us all to use a common set
of definitions and names.  All of the traditional units that are in
"common use" are definable in SI units.  example: one bar = 100 kPa
The pascal (Pa) is NOT an SI base unit, it is an "SI derived unit".
In terms of base units 1 Pa = (m^-1)(kg)(s^-2) ... easy, huh?

The only SI base units are:

quantity                   unit      symbol
length                     meter      m
mass                       kilogram   kg
time                       second     s
electric current           ampere     A
thermodynamic temperature  kelvin     K
amount of substance        mole       mol
luminous intensity         candela    cd

Everything else is a derived unit (or an unaccepted unit)!

The standard is available (free) via the NIST web site.

- Nick -

Sean Breheny wrote:
{Quote hidden}

1999\11\03@105935 by Sean Breheny

face picon face
At 11:56 PM 11/3/99 +1300, you wrote:
>While we're on the correctness kick - ALL SI units MUST be in multiples or
>sub multiples of 10^3.
>ie horrendous measures such as cm are forbidden.
>
>Angstrom is similarly almost forbidden except that, as it does not imply its
>multiplier (or its major unit) in its name it is not liable to confuse.
>However, use of centimetre will bring disaster on one's head sooner or
>later.
>

Well, actually, I guess if you want strict SI, perhaps cm is not used,but
the CGS (Centimeter-Gram-Second) system is far from dead,it is often used
in physics (especially atomic) and semiconductor device design (this is the
system with the erg,cm,statvolt,dyne,bar,etc.)

Also, the angstrom is kinda handy in some contexts because it is the
approximate mean diameter of an atom (I think it is based on hydrogen,but I
could well be wrong).

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
@spam@shb7KILLspamspamcornell.edu ICQ #: 3329174

1999\11\03@133324 by Harold M Hallikainen

picon face
On Wed, 3 Nov 1999 06:38:48 -0800 Nick Taylor <KILLspamntaylorKILLspamspamINAME.COM> writes:
>Russell,
>Do you have a reference for 10^1 and 10^2 units being forbidden?  I
>have the NIST Special Pub 811 (US) booklet in front of me and cannot
>find any such reference.
>
>Here is the list of terms that are "unacceptable":
>erg, dyne, poise, stokes, gauss, oersted, maxwell, stilb, phot, fermi,
>metric carat, torr, standard atmosphere, kilogram force, micron,
>calorie,
>x unit, stere, gamma, gamma (mass), gamma (volume).
>

       Thanks to this list, I did get the NIST publication.  Let's
see...  units above that I have used include erg (energy, as I recall),
dyne (I think that's force... as I recall, we measured pressure in dynes
per square centimeter), poise (a summer job was calibrating viscometers
where the viscosity of fluid was measured in centipoise), gauss, oersted,
and maxwell I recently (within the past five years) dealt with in
teaching an electronics class that included magnetics.  The calorie (not
the kcal or Calorie of dieting fame) is what I used in a junior high
school science fair project showing the relationship between watt-seconds
and calories, and showing the heat capacity of water.  So... what IS the
standard unit for energy now, if not the calorie?  Is it the watt-second?
       This also reminds me of an article by Bob Pease in a recent EDN
where he discusses light and the MANY measures of it.  Some are described
as units of brightness and others are intensity, both of which are
meaningless to me.  As I wrote in an email to him, it appears we are
either dealing with POWER (watts, or, more archaicly "candle") or POWER
DENSITY (watts per square meter, or, a more archaic unit, foot-candle).
In the email I argued that we keep the metric prefixes out of the
denominator of units.  Thus, it seems we should avoid power densities in
milliwatts per square centimeter, instead doing [insert prefix here]
watts per square meter.

Harold


Harold


Harold Hallikainen
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Hallikainen & Friends, Inc.
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