RE: SI Units

Subject: RE: SI Units
From: Deborah Snavely <dsnavely -at- aurigin -dot- com>
To: TECHWR-L <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Tue, 27 Jun 2000 11:10:33 -0700

One of the real challenges of standard units is that not all fields of
engineering use the *same* standards. And technical writing long since
expanded to cover more than any one field of engineering.

The electrical industry standard abbreviations for "volts alternating
current" and "volts direct current" are "Vac" and "Vdc" or "V ac" and "V
dc". But the semiconductor industry, the semiconductor equipment industry,
and hence the computer industry, have all chosen to ignore existing
standards and invent their own (I still suspect computer engineers' roots in
ALL CAPITAL code-writing for its prejudice in the matter of technical

So the Microsoft manual of style specifies "VAC" and "VDC", one of which
conflicts directly with the HVAC (Heating, Ventilation, and Air
Conditioning) industry standard of "VAC" meaning "vacuum."

And when I worked for a semiconductor equipment manufacturer (SEM), the Tech
Pubs department wrestled with such competing standards because their
equipment used electrical equipment, HVAC-related equipment, mechanical
engineering equipment, chemical equipment, computer hardware equipment, and
computer software...all on the same machines. So we *had* to standardize,
but we worked in an industry where most of the industry advertising and
white papers and technical journals used whatever "standards" the engineers
(usually sans writers or editors) invented on the spot, coming from their
particular training's preferences as to standards.

The whole SEM industry capitalizes the word TORR [sic] more often than not,
in despite of the term being correctly capitalized in your average American
dictionary (Torr). Tech Pubs there standardized on SI units and then had to
go as far as getting a confirming fax from the National Institute of
Standards and Technology that we'd applied the SI system correctly in
abbreviating "milliTorr" to "mTorr" (there is *no* single-letter
abbreviation for Torr, or wasn't in 1993) in order to get buy in from a
hardware engineer turned writer who was certain he knew the answers to
everything and they all came in ALL-CAPS.

>I learned, that a space ship lost its route because of ambiguities in
>measurement between several systems.

The most recent instance of that problem was the Mars probe that
crash-landed in 1999 because of two different software groups on the
project, one used meters and one used feet, and no one in charge of the
whole thing ever figured it out in advance. It took forensic documentation
digging after the crash to find out. (Sigh.)

Deborah Snavely, Senior Technical Writer, Aurigin Systems, Inc.

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