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7.3.6 Metric Units

(require 'metric-units) http://people.csail.mit.edu/jaffer/MIXF

Metric Interchange Format is a character string encoding for numerical values and units which:

In the expression for the value of a quantity, the unit symbol is placed after the numerical value. A dot (PERIOD, ‘.’) is placed between the numerical value and the unit symbol.

Within a compound unit, each of the base and derived symbols can optionally have an attached SI prefix.

Unit symbols formed from other unit symbols by multiplication are indicated by means of a dot (PERIOD, ‘.’) placed between them.

Unit symbols formed from other unit symbols by division are indicated by means of a SOLIDUS (‘/’) or negative exponents. The SOLIDUS must not be repeated in the same compound unit unless contained within a parenthesized subexpression.

The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable symbol (forming a multiple or submultiple of the unit concerned) which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols.

The grouping formed by surrounding compound unit symbols with parentheses (‘(’ and ‘)’) constitutes a new inseparable symbol which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols.

Compound prefix symbols, that is, prefix symbols formed by the juxtaposition of two or more prefix symbols, are not permitted.

Prefix symbols are not used with the time-related unit symbols min (minute), h (hour), d (day). No prefix symbol may be used with dB (decibel). Only submultiple prefix symbols may be used with the unit symbols L (liter), Np (neper), o (degree), oC (degree Celsius), rad (radian), and sr (steradian). Submultiple prefix symbols may not be used with the unit symbols t (metric ton), r (revolution), or Bd (baud).

A unit exponent follows the unit, separated by a CIRCUMFLEX (‘^’). Exponents may be positive or negative. Fractional exponents must be parenthesized.

7.3.6.1 SI Prefixes
            Factor     Name    Symbol  |  Factor     Name    Symbol
            ======     ====    ======  |  ======     ====    ======
             1e24      yotta      Y    |   1e-1      deci       d
             1e21      zetta      Z    |   1e-2      centi      c
             1e18      exa        E    |   1e-3      milli      m
             1e15      peta       P    |   1e-6      micro      u
             1e12      tera       T    |   1e-9      nano       n
             1e9       giga       G    |   1e-12     pico       p
             1e6       mega       M    |   1e-15     femto      f
             1e3       kilo       k    |   1e-18     atto       a
             1e2       hecto      h    |   1e-21     zepto      z
             1e1       deka       da   |   1e-24     yocto      y
7.3.6.2 Binary Prefixes

These binary prefixes are valid only with the units B (byte) and bit. However, decimal prefixes can also be used with bit; and decimal multiple (not submultiple) prefixes can also be used with B (byte).

                     Factor       (power-of-2)  Name  Symbol
                     ======       ============  ====  ======
            1.152921504606846976e18  (2^60)     exbi    Ei
               1.125899906842624e15  (2^50)     pebi    Pi
                  1.099511627776e12  (2^40)     tebi    Ti
                     1.073741824e9   (2^30)     gibi    Gi
                        1.048576e6   (2^20)     mebi    Mi
                           1.024e3   (2^10)     kibi    Ki
7.3.6.3 Unit Symbols
         Type of Quantity      Name          Symbol   Equivalent
         ================      ====          ======   ==========
     time                      second           s
     time                      minute           min = 60.s
     time                      hour             h   = 60.min
     time                      day              d   = 24.h
     frequency                 hertz            Hz    s^-1
     signaling rate            baud             Bd    s^-1
     length                    meter            m
     volume                    liter            L     dm^3
     plane angle               radian           rad
     solid angle               steradian        sr    rad^2
     plane angle               revolution     * r   = 6.283185307179586.rad
     plane angle               degree         * o   = 2.777777777777778e-3.r
     information capacity      bit              bit
     information capacity      byte, octet      B   = 8.bit
     mass                      gram             g
     mass                      ton              t     Mg
     mass              unified atomic mass unit u   = 1.66053873e-27.kg
     amount of substance       mole             mol
     catalytic activity        katal            kat   mol/s
     thermodynamic temperature kelvin           K
     centigrade temperature    degree Celsius   oC
     luminous intensity        candela          cd
     luminous flux             lumen            lm    cd.sr
     illuminance               lux              lx    lm/m^2
     force                     newton           N     m.kg.s^-2
     pressure, stress          pascal           Pa    N/m^2
     energy, work, heat        joule            J     N.m
     energy                    electronvolt     eV  = 1.602176462e-19.J
     power, radiant flux       watt             W     J/s
     logarithm of power ratio  neper            Np
     logarithm of power ratio  decibel        * dB  = 0.1151293.Np
     electric current          ampere           A
     electric charge           coulomb          C     s.A
     electric potential, EMF   volt             V     W/A
     capacitance               farad            F     C/V
     electric resistance       ohm              Ohm   V/A
     electric conductance      siemens          S     A/V
     magnetic flux             weber            Wb    V.s
     magnetic flux density     tesla            T     Wb/m^2
     inductance                henry            H     Wb/A
     radionuclide activity     becquerel        Bq    s^-1
     absorbed dose energy      gray             Gy    m^2.s^-2
     dose equivalent           sievert          Sv    m^2.s^-2

* The formulas are:

— Function: si:conversion-factor to-unit from-unit

If the strings from-unit and to-unit express valid unit expressions for quantities of the same unit-dimensions, then the value returned by si:conversion-factor will be such that multiplying a numerical value expressed in from-units by the returned conversion factor yields the numerical value expressed in to-units.

Otherwise, si:conversion-factor returns:

-3
if neither from-unit nor to-unit is a syntactically valid unit.
-2
if from-unit is not a syntactically valid unit.
-1
if to-unit is not a syntactically valid unit.
0
if linear conversion (by a factor) is not possible.
     (si:conversion-factor "km/s" "m/s" ) ⇒ 0.001
     (si:conversion-factor "N"    "m/s" ) ⇒ 0
     (si:conversion-factor "moC"  "oC"  ) ⇒ 1000
     (si:conversion-factor "mK"   "oC"  ) ⇒ 0
     (si:conversion-factor "rad"  "o"   ) ⇒ 0.0174533
     (si:conversion-factor "K"    "o"   ) ⇒ 0
     (si:conversion-factor "K"    "K"   ) ⇒ 1
     (si:conversion-factor "oK"   "oK"  ) ⇒ -3
     (si:conversion-factor ""     "s/s" ) ⇒ 1
     (si:conversion-factor "km/h" "mph" ) ⇒ -2