PPDM UNITS OF MEASURE
Contents |
Introduction
Identification of, and conversion between units of measure is critical to all scientific and technical work. Calculations and comparisons between values can only be made if the units are known. Many different units can be used to describe the same concept. For example, consider volumes. In North America, some of the commonly used units to describe volumes are fluid ounces, pints, quarts, gallons, barrels, milliliters, liters, kiloliters, cubic inches, cubic feet, cubic meters.
Depending upon the quantity being measured, the selection of units is somewhat narrowed -- the volume of oil produced by a well would not be measured in milliliters, nor would fluid samples used in a laboratory analysis be measured in cubic feet. However, even with consideration given to the quantity being measured, there are still many different units that could describe the same item. Therefore, a database containing measurements must clearly specify units. Nomenclature is inconsistent, as well:
- the same word can describe more than one quantity. For example, a gallon (US) is defined to be 231 cubic inches (3.785412L) while a gallon (British Imperial) is defined to be the volume taken up by 10 pounds of water (4.54609L).
- the same word can be used to describe more than one concept. For example, degrees measure both temperature and the arc of a circle.
- a lowercase letter may represent a different unit, or unit prefix, than an upper case letter. For example: s represents seconds, S, siemens; mW represents milliwatt, MW, megawatt.
- spelling can differ even when a unit is standardized. For example: liter versus litre.
- plurals may or may not be used.
- the same unit can be abbreviated in many different ways. For example, feet can be abbreviated as ft, ‘, F.
- compound units can often be written in different ways. For example m/s or m*s-1 .
The PPDM Units of Measure project was initiated by PPDM in 2003 in response to member interest, with the intent to develop a single, reconciled set of units of measure that could be used as a starter set for new implementations. Reference data was gathered from the international standards bodies, to provide member companies an inclusive set of units of measure, with conversion data for more common conversions. This data was supplemented by PPDM member companies with specific UOM needs. The reference data should not be considered absolute or permanent – many organizations have or will develop their own reference sets, tailored to their specific objectives, while PPDM plans to add additional conversion data.
Note
Production volume calculations are not covered in this guide, as these calculations are dependent upon external conditions, including temperature and pressure. Production volume calculation information can be recorded in the PPDM_VOL_% tables.
