This 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.
Soft metrication (or soft metric conversion) refers to the adoption of S.I. metric units for reporting, recording, or specifying all measurements, sizes, product dimensions, etc. Thus length dimensions would be reported in meters (or perhaps millimeters). However, no attempt is made to change the dimensions (sizes) of products such as fasteners, building materials, etc. to standard metric sizes (i.e., to adopt 25 mm bolts rather than 1 inch bolts).
Soft metric conversion also involves changing signage (speed limits, distances, etc.) and usually measuring devices (or adopting dual units capable measuring devices - e.g., electronic scales).
Soft metrication is generally much easier, cheaper and faster to adopt than hard metrication (discussed below) and is often used a step toward toward full (hard) metric conversion. Signage, package labels, reporting and dimensioning practices must be changed, metric capable (or dual units) measuring devices must be acquired, and personnel training will be needed. However, wholesale retooling of parts, fastener inventories, etc. is not required.
It is already the case that many packaged food items and most speedometers of U.S. automobiles are labelled in both U.S. customary and metric units.
There are several reasons for LBNL staff to adopt soft metrication:
Federal law (Metric Conversion Act of 1975 (PL 94-169, 15 U.S.C. 205) and the Omnibus Trade and Competitiveness Act of 1988 (PL 100-418)), Presidential executive order (EO 12770 of July 25, 1991), Federal Regulations (15 CFR 1170 - originally 15 CFR Part 19), DOE order, and LBNL policy (RPM Sect. 1.23) mandate the use of S.I. metric units.
Use of S.I. metric units facilitates scientific communication (esp. in international contexts). With the nearly the entire planet (except for the United States) using metric (S.I.) units, papers written using metric units can reach a much larger audience.
Use of metric units facilitates, e.g., kW for engine power, facilitates understanding of some issues of energy efficiency (e.g., of appliances).
The S.I. system of (metric) units is simpler. Thus energy (work) is always measured Joules (or some radix 10 multiple), whereas in customary units in the U.S. energy is various measured in BTUs (British Thermal Units), calories, foot-pounds, kWh (kilowatt hours), kilotons (of explosive energy), etc. Furthermore, some of these units have multiple variations, e.g., BTUs. Use of a single unit for energy measurements facilitates the teaching of the equivalence of thermal, mechanical, chemical, and electrical energy and the understanding of energy efficiency issues in the conversion of chemical energy to electrical or mechanical energy.
Consistent use of S.I. units is helpful in interdisciplinary studies (e.g., nanotechnology), avoids the proliferation of measurements units used in different subject domains of science and engineering, e.g., the various units used for energy and work across mechanical engineering, electrical engineering, physics, and chemistry.
Consistent use of S.I. units can prevent disasters such as the Mars Climate Orbiter, where misunderstandings about units caused the failure of a NASA Martian satellite.
Consistent use of S.I. units facilitates the interchange (esp. internationally) of medical records and medical research. It also reduces the possibility of medication errors due to units conversion errors or units misunderstandings.
Use of S.I. units for concentration (moles/cubic meter or more typically milli/micro/nano moles / liter) facilitates chemical computations and avoids the potential ambiguities of dimensionless measure of concentration (e.g., is parts per million a molar, mass, volume, or pressure ratio?).
Adoption of metric speed limit signage (km/h) and distance signage (m or km) and map annotations would facilitate safe driving on site by foreign visitors and students. Marking speed limits in true S.I. units, i.e., meters/second, would be even better, but automobile speedometers are not marked in meters/second.
Hard 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 mm (rather than 4 ft x 8 ft = 1219.2 mm x 2438.4 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 Myanmar (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-tariff trade barrier and thus inconsistent with official United States trade policy, which is committed to the elimination of such non-tariff 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-tariff 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 Myanmar are not major allies of the United States.)
At LBNL, the universal 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).
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 engineering 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/
I am also presently working on improving the recording of measurement units and dimensionality in metadata registries such as ISO 11179.
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.
The 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 converting 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. Also note that Japanese cups are 180 ml, whereas U.S. cups are 240 ml.(approx.) (per Wikipedia).
Below we have begun to construct a table of some conversion factors to S.I. units which we anticipate will be useful for LBNL staff.
| Unit | Equivalent S.I. metric Units |
|---|---|
| Angstrom | 0.1 nanometer |
| BTU | 1055 joules |
| BTU/hr | 0.2931 watts |
| inch | 25.4 millimeters (exact) |
| ounce (weight) | 28.35 grams |
| kilowatt hour (kWh) | 3.6 megajoules |
| megawatt hour (MWh) | 3.6 gigajoules |
| quad (quadrillion BTUs) | 1.055 exajoules |
| ton (U.S. short ton) | 907.2 kilograms |
Below we list activities which individual LBNL staff members can undertake to accelerate metrication:
Individual researchers can use S.I. metric units 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 default to the use S.I. metric units. Measurement units should be thoroughly documented in all programs, data exchange formats, database designs, and forms specifications.
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.
In their role(s) as journal editors and referees for journals, conferences, and research proposal review panels researchers can demand 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 appropriate 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, delicatessens, 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 (under LBNL policy) price and sell bulk foods (e.g., the salad 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. Temperature forecasts now given in both Celsius and Fahrenheit measurements.)
Individuals can adopt the use of metric fasteners in their personal furniture, mechanical, home construction or renovation.
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).
In our interactions with doctors and medical researchers we can urge the adoption of S.I. (metric) units for chemical concentrations, blood pressure, temperature, etc.
Those LBNL staff engaged in teaching and writing text books can adopt S.I. (metric) units.
LBNL staff can insist on the purchase of metric (or dual U.S. customary/metric) measuring devices (tape measures, calipers, etc.).
LBNL staff engaged in the procurement of motor vehicles can specify vehicles which use exclusively standard metric sized fasteners. (As motor vehicle production has become internationalized this is becoming easier. Thus most motor vehicle engines now use metric fasteners.)
Procurement of bulk commodities at LBNL can be specified in metric units (oil, chemicals, cement, etc.). Concentrations of chemicals purchased should be specified in moles/liter (molarity).
LBNL staff can format all of their documents with margins consistent with both U.S. paper size (216 mm x 279 mm)(8.5 x 11 inches) and metric A4 paper size (210 mm x 296 mm).
Dimensionality 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. Furthermore, it is desirable to record the temperature and pressure conditions under which the concentration measurements were made.
Other, commonly used, conventions for concentration include:
Note that mass, volume, molar, and pressure ratios all appear to be dimensionless. However, they are not directly comparable. Conversion among the various concentration measures requires knowledge of the material properties, and the environmental context (temperature and pressure).
It appears that unannotated concentration reporting as "ppm" usually means mass ratios, but not always.
Conversion 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 (not easily done in Berkeley).
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 accommodate A4 paper. Bookshelf spacing may also need to be adjusted.
I would like to thank Chris Marnay for his helpful comments and continuing encouragement. Chris provided me with initial resources on metric conversion. Vladimir Bazjanac has also provided encouragement. The Energy Efficiency Standards Group in the Energy and Environmental and Technologies Division continues to incite me with their failure to adopt S.I. metric units in the energy efficiency standards. Thanks also to Ron Bessette who corrected some errors in plywood dimensions. Pat Naughtin provided additional resources and prompted me to update this web page recently (2006-08-05).