PentaCalc Pro's Smart Units is a complex method of evaluating units. Most of this complexity is transparent to you as the user. However, occasionally, you may need to "lift the hood" and create your own units. Fortunately, creating new unit conversion buttons and configuring Smart Units is a rather straight forward process. To create a new unit, you must first understand what makes Smart Units "tick."
Smart Units are composed of a hierarchal structure: type, base, and unit. Each base and unit must be composed of atomic units. Atomic units are units which have been reduced to their elemental form. Atomic units can be found in ten calculators we ship with PentaCalc Pro: Temperature, Length, Mass, Time, Substance, Luminance intensity, Currency, Current, Angle and Solid angle.
Within each of these ten calculators, there is one unit that is unique and has earned membership in the Special ten group. (All other units within these ten calculators are both special and atomic, but they are not as special as the Special ten.) The Special ten consist of a modified S.I. base. In addition to the seven base S.I. units ( Length-meters, Mass-kilograms, Thermodynamic temperature-kelvin, Electric current-amperes, Luminous intensity-candela, Amount of substance-moles and Time-seconds) we have included the supplementary S.I. base units (Plane angle-radian and Solid angle-steradian). Finally, we added a non S.I. unit (Currency-US dollar).
The base must be composed of a combination of Special ten units only, while a unit may be composed of any atomic unit (meaning a unit must be composed of units from any of the ten calculators mentioned previously in this section). In general, bases provide a way to separate units into systems such as S.I. and English. There will generally be one base per system in each unit type.
Bases exist for two reasons:
They allow more accurate conversions. For example, 12 inches = 1 foot and 3 feet = 1 yard exactly. Instead of listing all units in terms of the Special ten unit, meters, where the conversion factors are often long and imprecise, they are listed in terms of their base where the conversion factors are usually exact. Conversions between units of the same base will often be more precise than if you cross bases.
It is easier and more convenient to create units in terms of a base because the conversion factors are better know. For example, you know how many feet are in a yard, but generally you don't know how many meters are in a yard.