The Chain Gang

By The Metric Maven

Bulldog Edition

When I was taking a machine shop class, I was the lone metric advocate. There were in fact rounds of boos when I first brought the subject up. One of the instructors decided to plumb the depths of my ignorance with this question “What units are used to construct roads in the US?” To his surprise I replied “chains, and that makes sense how?”

Originally sections of a chain were used to measure land. Later the length of these chains were decimalized. A chain has a length of 100 feet (US Survey Feet) with each link in the chain equal to one foot. Each foot is then divided into ten parts. This is called an Engineer’s Chain or Ramsden’s Chain. But, most of the country was surveyed with Gunter’s Chain according to what I’ve read. According to Wikipedia:

The chain is divided into 100 links, marked off into groups of 10 by brass rings which simplify intermediate measurement. Each link is 7.92 inches long, with 10 links making slightly less than 6 feet 8 inches. The full length of the chain is 66 feet.

Gunter’s chain reconciled two seemingly incompatible systems: the traditional English land measurements, based on the number 4, and the newly introduced system of decimals based on the number 10. Since an acre measured 10 square chains in Gunter’s system, the entire process of land measurement could be computed in decimalized chains and links, and then converted to acres by dividing the results by 10.

Got that? Well, I don’t, so I decided to call someone who does this for a living. I spoke with a Colorado Surveyor who works on public roads. Modern chains are not made of chain, but are now steel tape measures. When a measurement is under 100 feet, its accuracy is generally best determined with a chain tape. For measurements over 100 feet, Surveyors use an Electronic Distance Meter (EDM). Beyond about 1/2 mile they switch to GPS.

Surveying Chain Tape

The Surveyor indicated that because GPS is a meter based system, the Surveyors measure out all the distances in meters, but then immediately convert them to survey feet. If there is data that is not immediately converted, this is the first step done when it is imported into a Computer Aided Design (CAD) system. The design is then done all in feet.

As we talked, the Surveyor interjected: “I would much rather do everything in metric, and in the 1990s it looked like that would happen.” He explained that the US DOT had mandated the use of metric in the late 1990s. Colorado created and printed up specification books in metric and had them printed—at no small cost. The surveyors began to measure and build in metric. Metric was then met with “resistance” whose origin he could not specify. There were complaints about “machines” all being in inches, and horrible calibration problems. This sounds like the “any excuse we can think of not to change, no matter how ridiculous” method of stopping metrication.  The Feds reversed themselves and said go ahead and go back to the way you were doing it—we’re still not ready for metric. Now well into the second decade of the 21st Century, we are back to using decimal feet to measure our public construction. The same way we did it in the 19th Century.

Then I was surprised by this revelation: The road people have one heck of a time dealing with the bridge designers. This is because, instead of using decimal feet, bridges are designed in feet and inches. One can imagine plenty of room for error and confusion with this situation. Of course if it was all in metric—no such problems.

Architectural firms in the US use feet and inches, yet around the world construction is done in metric. There is no study, of which I’m aware, that investigates how much international construction work may be lost, because other countries don’t want designs bid with imperial units. A UK Metric Views Contributor John Frewen-Lord asserted that there may be a metric reason that US firms are buying up established UK civil and structural engineering consultants:

Although many projects are designed by nominally US companies, most work is done by a local office using local people familiar with SI. In my experience as a quantity surveyor working internationally, the US offices of these companies are woefully unfamiliar with SI. I remember when I was once in Chicago, in SOM’s (Skidmore Owings Merrill) offices, looking over a project to be built in the Middle East. It had obviously been conceptually designed in SOM’s Chicago offices in USC, which they then ‘converted’ into SI – to about 10 decimal places! Ridiculous – not only dimensioning everything to an accuracy of micrometres, but the fact that the resulting sizes and dimensions were wrong for metric products (everything from blocks to light fixtures). SOM’s local office in Riyadh had to re-dimension the building.

Our lack of a coherent measurement system has long ago become an economic ball and chain which impedes US industry and commerce. It is long past time for the United States to reform our weights and measurements, switch to metric, and coordinate their usage across all government agencies and mandate metric for the nation as a whole. We just can’t afford to continue doing otherwise.

US Electronics: A Metric Peg in an Imperial Hole

By The Metric Maven

Bulldog Edition

The Metric Maven has read countless articles about the decline of American electronics manufacturing. Pundit after Pundit who almost certainly have no idea which end of a soldering iron to pick-up, feign deep knowlege of what makes us “uncompetitive.”  There is always a laundry list of problems which are trotted out by these professional opinion manufacturers. The one item which is never on their list, is the lack of the metric system in the US. This omission is proof by proxy they are armchair commentators who know a thousand ways to make love to a woman, but have never had a girlfriend.

Central to the miniaturization of electronics in the 21st century is the surface mount device (SMD). They are packed into smaller and smaller sized printed circuit boards. This makes “smart” phones, and other devices smaller, and much easier to lose–I mean use. The world standards groups met long ago and defined SMDs in terms of metric. Industry PCB consultant Tom Hasherr sees it this way:

The United States is now the only industrialized country in the world that does not use the metric system as its predominant system of measurement.

All the World Standard Groups involved in the electronics industry (IPC, IEC, NIST, JEDEC, EIA & JEITA) have made the transition to the metric measurement system. They formed an alliance to stop using English units and all the data they publish is in metric units.

Buried within these diplomatic statements is a larger story of America looking down, taking direct aim, and shooting itself in the foot—with inches.

The story goes like this: Once upon a time in the 1980s the world standards organizations banded together and produced worldwide metric standards. The Electronics Industries Alliance (EIA) in the US was given the responsibility to articulate the size of surface mount devices. The world had created all the standards in metric, and the EIA was to publish the new dimensions for all to use. A book was printed with all the component names, dimensions and other pertinent engineering data. It was then released to US manufacturers for implementation.

American component manufacturers refused to make components to metric dimensions. The PCB assembly and etching houses rejected metric dimensioned drawings, and spurned any thought of using them. They repeatedly demanded the EIA publish a version of the standard with Imperial (English) units. The EIA finally did this and unilaterally changed the names of the components.

The metric SMD components were now renamed using inches. Originally, the first two numbers of the chip component names are the SMD length in mm, and the second two are the width in mm. There is an assumed decimal point between each set of paired numbers. For example 3216 is 3.2 mm x 1.6 mm. Here is a short list of the renaming:

Now the 3216 is renamed 1206 which is 0.12″ x 0.06″ with an assumed decimal point at the front, and whatever conversion factor error is introduced. We can see that this US “improvement” introduced the same name designation for different sized electronic SMD components. After this re-naming, should you be interested in an 0402 or 0603 device, one now has the opportunity for a metric/imperial nomenclature mistake, which could precipitate lost time and money.

When the world standards committees discovered what the EIA had done, they released an order for the EIA to cease publication of this non-metric document. The EIA was reminded they were in violation of the international agreement they signed with all the world standards bodies agreeing NEVER to publish ANY standards using Imperial (English) units. In 1991 the EIA stopped publishing the feral document, and it is my understanding, that because of this, there is no longer any official standard  followed in the US.

The US component manufacturers and PCB etching houses returned to the days of the perch, furlong, and barleycorn. With no standard to follow, SMD manufacturers began to game the situation. There were no longer standards for capacitors or inductors, or common three leg transistors known as SOT23.  So 20 different sizes of these small outline transistors (SOT23) appeared. Chaos ensued. Rather than impose order by standards regulation, or metric adoption, the US industry just tried to figure out a way to name the multitude of these ad hoc non-interchangable “standard” parts.

The rest of the world embraced metric measurements and metric standard electronic parts. If you are in Germany and order parts from Japan, or Korea, or Timbuktu, you know they will fit on your printed circuit board. These are all metric countries.  You have no guarantee if you order American electronic surface mount parts, that they will fit. If you were a German, would you take the chance?

The situation is actually far worse than I have explained thus far. In the United States our PCB software puts down grids in mils (a feral unit of the inch) or in inches. The world standard for parts is metric. The standard grid size for which these parts are designed is 0.05mm, so there is no reason to expect the metric parts to fit nicely on an inch based software grid. They are two different measurement units! The software used to connect up parts makes many mistakes in a mixed imperial/metric environment. We often have to fix these “by hand.” There is no guarantee of compliance to layout standards when metric and imperial are mixed. Metaphorically, we are trying to fit square pegs into a set of round holes. Metric parts on a metric grid are interconnected by software to international standards.

Vacuum Tube SchematicOver the last decade, I’ve watched as one small US based printed circuit board house after another have gone out of business. The company where I last had full-time employment, picked up and moved to China. How much of this PCB work might have remained in the US if we had embraced the metric system years ago? It’s hard to say, but it should be clear that metric conversion is of paramount importance—period. Unfortunately, the idea of industrial policy disappeared as a government concept in 1980, along with metric conversion, and has not been contemplated since.

When construction, medical, electronics and other industries are all taken together, one has to wonder just how much it has cost us not to have mandated the metric system in the United States. There were legislative efforts to make metric the official measurement system of the US in 1866, 1902, 1921, and 1975, and they were all either rejected by Congress, or were voluntary and therefore impotent.  We may never know how much it has cost the country, because the US may never become metric.

The technically ignorant pundits who populate our media space, will continue to point to reasons that are divorced from any understanding of Engineering, technology, manufacturing, or the metric system as a problem with US manufacturing “competitiveness,” and the rest of the world will  continue to reap the benefits of their choice to become metric—decades ago.

Related essay:

The Cuprous Proxy