Metrication (Adoption of SI Metric Units)IntroductionThis web page is concerned with metrication (adoption of S.I. (metric) units) at Lawrence Berkeley National Laboratory. Laboratory policy is that we should conduct all research in S.I. metric units at all times, record all measurements in metric units (e.g., in databases), and report (publish) all research results in metric units. Translations to other measurements units may be indicated in parentheses following metric units, and only when essential for audience understanding. Furthermore, we are supposed to adopt the use of S.I. metric size standards (i.e., ISO size standards) for all fasteners, machinery, construction, etc. Details can be found below. Why Metrication?Soft MetricationSoft metrication (or soft metric conversion) refers to the practice of the reporting all measurements in metric (S.I.) units, but not changing conventional size standards (selling liquids as quarts but noting converted volume in liters, retaining customary sizes of construction materials, U.S. customary unit based screw threads, etc.) Soft metrication is much easier and cheaper to adopt than hard metrication (see below) since only measuring devices, writing, and drafting practices need to be changed - not wrenches, fastener inventories, etc. There are several reasons for LBNL staff to adopt soft metrication:
Hard MetricationHard metrication (or hard metric conversion) extends soft metrication (the reporting all measurements in metric (S.I.) units) to the adoption of metric based size standards (usually ISO standards) for packaging, construction materials, screw and bolt threads, bolt diameters and heads, piping sizes, paper sizes, etc. Thus one would sell milk (or oil) in liter, rather than quart containers, adopt plywood panel sizes of 1200 mm x 2400 (rather than 4 ft x 8 ft = 12019.2 mm x 24038.4 mm), use metric standard screw threads, bolt sizes (e.g., 25 mm vs 1 inch (25.4mm)), etc. Hard metrication is considerably more difficult and more expensive since it requires changes in packaging, tooling, fastener and some other parts inventories (plywood, etc.) inventories. However, virtually all of the world economy except for the United States is now on hard metric size standards. (Liberia and Myanamar (Burma) also use non-metric units.) Hence the use of U.S. customary unit based sizing for packaging, construction materials, threads, bolts, etc. is effectively a non-tarriff trade barrier and thus inconsistent with official United States trade policy, which is committed to the elimination of such non-tarriff trade barriers (in principle at least). In any case international trade in autos, machinery, etc. effectively means that continued use of customary units based sizing in the U.S. will require us to continue to maintain dual sets of tools, wrenches, etc. Hard conversion would (eventually) permit us to dispense with dual tooling, fasteners inventories, etc. Of course elimination of such a non-tarriff trade barrier would offer the usual advantages of increased international competition and (presumably) reduced prices. Note that adoption of metric size standards would also permit U.S. manufacturers to produce a single set of products for both domestic and international sale, offering them additional economies of scale. For those manufacturers which presently produce only equipment to inch-based size standards, adoption of metric based (i.e., ISO) size standards would ease acceptance of their equipment in overseas markets. Hard metric conversion will also facilitate interoperability of U.S. military forces with allied forces - since all of our allies are now using metric size standards for machinery. (Liberia and Mynamar are not major allies of the United States.) At LBNL, the adoption of hard metric standards for design of experimental equipment would facilitate integration of LBNL designed equipment into international scientific collaborations, e.g., CERN, which rely on metric sizing and fasteners. U.S. law, executive and D.O.E. orders cited above also mandate the adoption of hard metrication (albeit at a slower pace and with more exceptions). Resources
LBNL Metrication Contacts
Why do I care?Why would a database researcher care about issues of measurement units? The basic answer is that I am interested in technologies for facilitating the sharing of data, especially scientific and engineeering data. The adoption of common measurement units (e.g., SI metric units) is a major step forward in facilitating such sharing of data. Issues of measurement units and dimensionality are important aspects of the semantics of data, and should included in the design of all database systems and data exchange formats. However, current practice in most database management systems and databases is abysmal, with measurement units often inadequately documented and dimensional consistency rarely enforced. Thus it is perfectly legal in SQL to add mass and length together, even though is obviously nonsense. I have been (and continue to be) interested in issues around the specification of dimensionality and measurement units in databases and in data exchange formats. I am occasionally working with Bob Dragoset of NIST on development of XML markup language of measurement units and creation of a measurement units registry at NIST. The XML markup language for measurement units will be known as UnitsML . See these two web sites: http://pueblo.lbl.gov/~olken/mendel/units/units.htm and http://unitsml.nist.gov/ Finally, I continue to be interested in issues around the specification of data exchange formats. Variant measurement units are a major obstacle to the reliable exchange of data among various databases and applications. U.S. Customary Units vs. U.K. Imperial UnitsThe careful reader may have noted that I use the term U.S. customary units rather than English units or (U.K.) Imperial units. This is because Imperial units are NOT identical with U.S. customary units. In particular, volumetric units, e.g., gallons, quarts, pints, ..., differ between U.S. customary units and Imperial units. Also, the U.S. ton is 2000 pounds (short ton) whereas the U.K. ton is 2240 pounds (long ton). U.S. customary units are sometimes referred to as Inch-Pound units, e.g., by ASHRAE and ASME. Users should exercise care when convering volumetric measurements from U.S. customary units to S.I. metric units to be sure that they have conversion factors for U.S. customary units rather than Imperial units. Some Conversion FactorsBelow we have begun to construct a table of some conversion factors to S.I. units which we anticipate will be useful for LBNL staff.
What is to be done?Below we list activities which individual LBNL staff members can undertake to accelerte metrication. Individual researchers can use metric (S.I.) in their publications, standards writing, and web pages. If some readers need U.S. customary units, use dual units for measurements, writing non-metric dimensioned measurements in parentheses following metric dimensioned measurements. Consult NIST documents for metric style usage. Software designers and database designers can adopt the usage of metric units for storage and computation with dimensioned units. Input and output should by default use S.I. (metric) units. Individual researchers can also call their colleagues attention to their usage of non-metric units and urge them to convert to S.I. (metric) units. Supervisors can require usage of metric units by their subordinates in publications, software and databases. Mechanical and civil engineers can dimension drawings in metric units. They can design to ISO hard metric standards for machinery (this may be harder for civil engineers). Metric paper sizes can also be adopted for engineering drawings. Purchasing agents can identify vendors which carry and catalog metric dimensioned parts, supplies, and equipment. They could require contract vendors (office supplies, scientific supplies) for LBNL to stock metric size fasteners, containers, materials, paper, etc. It is currently difficult to obtain metric paper sizes (A4) at LBNL. Technical editors at LBNL can call attention to use of non-S.I. units, and suggest the use of approprite S.I. units. Authors, editors, and compositors at LBNL can select page margins which facilitate the printing of LBNL technical reports on either U.S. customary paper sizes or A4 sized paper. Alternatively, multiple .pdf files can be generated - one for U.S. customary paper size, one for A4 paper size. (See discussion below.) Individuals can repeatedly ask grocery stores, produce vendors, delicatessans, butchers, coffee, tea, and spice vendors to price and sell bulk items in S.I. metric units. One can also ask for the provision of metric scales at food stores. Specifically, the LBNL cafeteria should be reminded that it is supposed to price and sell bulk foods (e.g., the sald bar, bulk candy, etc.) in metric units (and provide metric scales). Readers can contact the editor of LBNL Today to urge that they publish the daily weather statistics in degrees Celsius rather than degrees Fahrenheit. (This has been done.) Individuals can adopt the use of metric fasteners in their personal furniture, mechanical, home construction or rennovation. Individuals can give metric measuring instruments / utensils to friends and family as gifts. One can give (or post) directions in metric units (meters or kilometers). Recording Chemical ConcentrationsDimensionality and measurement units for recording chemical concentrations are a complicated (and often badly done) affair. S.I. (metric) conventions for measurement units of concentration are to record moles per cubic meter (or commonly molar concentration of moles/liter abbreviated M). All LBNL recording and reporting of concentrations, including in software, should observe the SI convention. Other, commonly used, conventions for concentration include:
Use of metric paper sizesConversion to the use of standard metric sizes of paper is likely to be easier than other forms of hard metric conversion, since paper is (mostly) a consumable, reducing requirements for maintaining inventories of traditional paper sizes. Standard metric paper sizes and their rationale are discussed at the web site International Standard Paper Sizes by Markus Kuhn. The most common standard metric paper size is A4 (210 x 297 mm), which is similar in size to U.S. conventional paper sizes of 215.9 x 279.4 mm (8.5 x 11 inches). A4 paper is slightly longer and narrower than 8.5x11 paper. In practical terms it is desirable to choose margins and text widths for paper formatting which can work on both A4 and 8.5x11 paper sizes, i.e., narrow enough to fit on A4 and short enough to fit on 8.5x11. PDF files normally carry embedded information of the preferred paper size (requiring manual intervention at the printer to change). Hence, it is common to post duplicate versions of papers in PDF format - one for A4 paper and one for 8.5x11. Most printers and copiers are capable of handling A4 size paper if you can find a supply of it. Perhaps more seriously, different binders, file folders, and filing cabinets will be needed if A4 paper is widely adopted. Note that U.S. legal size folders, file drawers, etc. can accomodate A4 paper. Bookshelf spacing may also need to be adjusted. AcknowledgementsI would like to thank Chris Marnay for his helpful comments and encouragement. This page is maintained by Frank Olken Last update: Tuesday, 2004-907-20 |