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The Metric System: It’s a Fact of Life so Why Not Get It Right?

Europe is getting particularly snotty
about the metric system. According to the National Institute of
Standards and Technology (NIST), all products sold in the European
Union (EU) and its associated countries must be specified and
labeled only in metric units. Dual units on product labels
will no longer be permitted in any European country. This means
U.S. exporters will no longer be able to sully the labels of their
products with units such as inches, pounds, or two kinds of
ounces.

Now don't get me wrong. I am not one of those metrication cranks
who think Americans should be forced to stop using our customary
versions of Imperial units. I think it's cool that horses are
measured in “hands” and horse races in furlongs, bullets and powder
charges in grains, nautical distances and depths in nautical miles
and fathoms, jewel sizes in carets, type sizes in points and picas,
air conditioners in BTUs, firewood in cords, and apples in
bushels.

The United States has been a metric country since the 1860s when
Congress passed a law allowing anyone to use the metric system
if they wanted to . When I took this stance once before
publicly, I was bombarded with actual hate mail from metrication
cranks. One stated that he was going to “straighten me out,” to
which I politely replied that “straightened out” I measured 6 feet,
1 inch long and that I expected to be buried 6 feet under when I
died. Generously, I added that if he wanted to be buried 2
meters/metres (either spelling is allowed) under, it was OK by
me.

In my job I see hundreds of emanations from US electronics
companies every week. I long ago gave up being surprised at how
badly US engineers mangle the metric system. For example, one large
US semiconductor, who shall remain nameless, publishes
specifications for its devices in two-column tables on its Web
site. In the left-hand column the company abbreviates nanoseconds
as nsec, and in the right-hand column it uses nS. Neither is
correct [!]—ns is the correct abbreviation for nanoseconds,
and nS stands for nanosiemens, the unit of conductivity. Most US
electronics companies do around half their business overseas where
the metric system is the norm, so mistakes like these don't look
good.

The metric system sure looks like it's here to stay. The United
States is signatory to international treaties about the metric
system, and it's all spelled out in an ANSI standard, SI-10. So
there is really no excuse for getting it wrong. Get a copy of the
standard and make it part of your company's style guide.

Right off the bat, the first thing to do is to start calling it
by its right name. It's not the metric system: it's The
International System of Units, universally abbreviated SI (from the
French Le Système International d'Unités ). The SI
was established in 1960 by the 11th General Conference on Weights
and Measures (CGPM, Conférence Générale des Poids
et Mesures
).

Next, US engineers need to be disabused about some SI units that
do not, in fact, exist. You would never know it from US
publications, but there is no such unit as the micron (abbreviated
µ) any more. Virtually every publication about semiconductors
talks about this or that micron process. Well, surprise! The gnomes
who decide such things have decided that the venerable micron has
been replaced with the micrometer (µm) to bring it in line
with other SI units.

Ditto for degrees kelvin (abbreviated °K). When
abbreviated, kelvin does not take a degree sign; it's abbreviate
just plain capital K. I realize the whole capital-K vs.
lower-case-k thing is hopelessly confused, but under the SI,
lower-case k, not upper-case K means a multiplier of 1000.

Actually the rules for when to capitalize an abbreviation are
pretty simple. If the unit is derived from a person's name, it is
capitalized when abbreviated and lower-cased when spelled out. So
it's V for volt (not Volt), F for farad (not Farad), for ohm
(not Ohm), A for ampere (not Ampere), and so on. Units not derived
from people's names are always lower-cased whether spelled out or
abbreviated. Hence it's s for second, m for minute, and so on.

Multipliers of a million and above are upper-cased when
abbreviated and lower-cased when spelled out, so it's MW for
megawatt but kV for kilovolt. There is never any punctuation
between multipliers and units, and the multiplier goes up against
the unit, not the number. In other words, milli-amps and Kilo Volts
are wrong.

Well, now that I have explained the SI, I expect everybody to
get it right from now on.

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