[SI-LIST] : that pesky mil problem

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From: Andy Peters (apeters@noao.edu)
Date: Thu Nov 04 1999 - 15:34:55 PST


I sent a comment to our sysadmin about this whole mil-spec thing and he sent
me the following:

 Bug Id: 4153347
 Category: utility
 Subcategory: conversion
 State: integrated
 Synopsis: units: misc bugs and deficiencies
 Description:
richard.mathews@West 1998-06-29

PSARC/1998/252 approved adding a bunch of new names to units and unittab.
This
included currencies such as "euro", prefixes such as exa- (10^18), aliases
for existing units such as "metre", new units such as "sievert", and new
physical constants such as Newton's Universal Gravitational Constant, "G".
A few misspelled or obsolete units were deleted by that PSARC case.

In addition to implementing the changes from the PSARC case, there are
a number of bug fixes needed. These are:

Corrected unit:
        < rontgen 2.58-4 curie/kg
> rontgen 2.58-4 coul/kg
        (Using standard abbreviations, the unit would be written as C/kg.
        Somebody probably mistook C to mean Curie (for which the symbol
        is actually Ci). Given that Curies and Roentgens both relate to
        radiation, it is an understandable mistake. Roentgen actually
        measures the ionization produces by the radiation, so Coulomb
        is actually the correct unit.)

Corrected value:
        < mil 1-2 in
        < mil 1-3 in
        A mil is a thousanth of an inch (10^-3), not a hundredth.

Updated values which are now EXACT:
        < c 2.997925+8 m/sec fuzz
> c 2.99792458+8 m/sec
        (Yes, this is exact. The meter is now defined to be the distance
        a photon travels in a vacuum in 1/299792458 second).

        < brgallon 277.420 in3 fuzz
> brgallon 4.54609 litre

        < brpeck 554.84 in3 fuzz
> brpeck 9.09218 litre

Units that should be defined exactly in terms of other units
        < atomicmassunit 1.66044-27 kg fuzz
> atomicmassunit gm/mole

        < britishthermalunit 1.05506+3 joule fuzz
> britishthermalunit cal lb-degF/gm-degC

        < rankine 0.555556 kelvin
> rankine 5|9 kelvin

Updated values based on currently accepted experimental data:
        In notes to each of the following, a 2 digit number in parentheses
        indicates the uncertainty in the last 2 digits of the preceding
        number.

        < au 1.49597871+11 m fuzz
> au 1.4959787069+11 m fuzz
        (published measurements include ...70680(30) and ...70700(30))

        < year 365.24219879 day fuzz
> year 365.2421896698 day fuzz
        (value stated by the Astronomical Almanac:
           365.2421896698 - 0.00000615359 T - 7.29E-10 T^2 + 2.64E-10 T^3
        where T is the number of 36525 day centuries since noon Jan 1 2000
UT.
        The old value was the one that used to be used for the year 1900.)

        < mole 6.022169+23 fuzz
> mole 6.022137+23 fuzz
        (value stated by NIST: 6.0221367(36) * 10^23)

        < e 1.6021917-19 coul fuzz
> e 1.6021773-19 coul fuzz
        (value stated by NIST: 1.60217733(49) * 10^-19 coul)

        < k 1.38047-16 erg/degC
> k 1.38066-23 joule/degC fuzz
        (value stated by NIST: 1.380658(12) * 10^-23 joule/degC)

        < rydberg 1.36054+1 ev
> rydberg 13.605698 ev fuzz
        (value stated by NIST: 13.6056981(40) ev)

        Also update all other currencies not listed above with new values
        based on the conversions listed in the 5/22/98 L.A.Times (except
        the value of the Luxembourg franc was obtained from CNNfn).
        Currencies that are to be based on the euro are written in
        terms of the euro; all others are still written in terms of the
        dollar. The comment in unittab says that the currency table was
        last updated in May, 1977. It isn't worth updating it often, but
        once every 20 years doesn't sound unreasonable:-)

Changed the definition, but the value is unchanged
        < pi 3.14159265358979323846
> pi 3.14159265358979323846 fuzz

        < dry 268.8025 in3/gallon fuzz
> dry 268.8025 in3/gallon

        < rad 100 erg/gm
> rad 1-2 gray
        (Grays and Sieverts both measure radiation doses, and both are
        equivalent to Joule/kg. The difference is that a Gray measures
        the actual energy deposited in each kg of the target while a
        Sievert measures the amount of damage the radiation does to a
        particular biological system by comparing it with how many Grays
        of dosage from a standard type of radiation it takes to do the
        same amount of damage. Defining the rad in terms of Gray makes
        it more clear which type of dose measurement a rad is. Note
        above that one of the added units is a rem which is defined as
        "1-2 sievert", making clear the difference between a rad and a
        rem.)

 Work around:

        Integrated in releases: s998_19
 Duplicate of:
 Patch id:
 See also:
 Summary:

-----------------------------------------
Andy Peters
Sr Electrical Engineer
National Optical Astronomy Observatories
950 N Cherry Ave
Tucson, AZ 85719
520 318 8191
apeters@noao.edu

"Creation Science" is an oxymoron.

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