Unit Names in Calchemy
The unit names and abbreviations recognized by
the Web version of Calchemy are indexed by category in the
Unit Definitions frame or page.
Names and abbreviations separated by commas (on the same line)
refer to the same unit definition and are case sensitive.
Each of these units may be used in any combination with others to form compound units
at will. For instance to enter a speed like "75 miles per hour"
you could type "75 miles/hour" or "75 mi/hr" or use the defined
abbreviation "75 mph". Compound units can be as complex as you need, like
"(kg(m/s)^2)/fortnight". You can even mix units from different systems like
"bushel/hectare" or "kg/ft^3".
NOTE, you will not see compound units (like newton/m^2) in the lists of defined
units because they are derived, not defined. However derived units with their own
names (like Pa) are listed.
Calchemy implements SI prefix rules, including all of the SI prefix
names and abbreviations. For example "mg" is the combination of "m" for
"milli" and "g" for "gram", not a separately defined unit. As a result
you may also express the unit as milligram, milli gram, m gram
or even millig.
NOTE, again you will not see prefixed units in the lists of defined units as
they are unit modifiers.
Pluralization of units
Calchemy implements a basic set of pluralization rules that are applied to
the interpretation of unit names. For instance you may use the
plural "miles" instead of "mile", "feet" instead of "foot" or even "henries"
instead of "henry". In general Calchemy does not accept plural forms
Secondary Definitions or "Overloaded units"
Some unit names traditionally have more than one common
use, such as "ounce", which can be a unit of mass, force, or volume.
We call these "overloaded units".
In most cases you may use the traditional name and Calchemy will make
a determination of what you mean based on a dimensional
analysis of the equation. Calchemy accepts four different overloaded
units, they are "pound, lb", "gram, g", "ton", and "ounce, oz". They all
may be either mass or force, ounce may also be a volume. If you want
to be explicit use an "m", "f", at the end of the unit name to specify
mass or force, ie: "poundm" or "poundf". To specify "ounce volume" you may
"Free units" are units that are not actually understood by Calchemy,
except that they are new and unique dimensions which must cancel out
in the end. For example in the equation:
2000 lbf * 60 mph / 4 wheels ? hp/wheel
= 80 hp/wheel
wheel is a free unit which Calchemy accepts because it cancels out. The acceptance
of free units makes using Calchemy more intuitive.
In Calchemy you can specifiy certain physical properties of materials
using the following conventions to identify the property and the material:
(xxx identifies the material, so the density of water would be dens_water)
dens_xxx identifies the mass density
hfm_xxx identifies the heat of fusion by mass
hfv_xxx identifies the heat of fusion by volume
hvm_xxx identifies the heat of vaporization by mass
hvv_xxx identifies the heat of vaporization by volume
hcm_xxx identifies the heat of combustion by mass
hcv_xxx identifies the heat of combustion by volume
hsm_xxx identifies the specific heat by mass
hsv_xxx identifies the specific heat by volume
ss_xxx identifies the speed of sound
tc_xxx identifies the thermal conductivity
te_xxx identifies the thermal coefficient of expansion
visc_xxx identifies the viscosity
The Windows version of Calchemy contains several lists of unit definitions including
the physical properties of many materials, obscure units (like barleycorns etc.),
properties of the solar system, energy content of fuels etc. In addition, in the Windows
version you can add your own unit definitions and unit name abbreviations.
Calchemy Software Inc.
Fort Collins, CO
Last Updated 6/21/2009
© Copyright 1996-2009 Calchemy Software Inc.