Category Archives: Manufacturing

Maintaining standards: The triple-point cell

Our society depends on standards in countless, mostly invisible ways.   If we can’t agree on how to measure weight, length, temperature, or time we can kiss manufacturing and our manufactured world with its specified, engineered, and interchangeable parts goodbye.   Actually creating and maintaining these standards is hard and the methods change over the years.  The meter was once defined in relation to earthly distances until the realization that the earth changes over time.  Now it is defined in relation to the speed of light which we are pretty sure does not.  The second used to be defined in terms of the day, now it is based on a fundamental property of the cesium atom.  The kilogram has just been redefined in terms of Planck’s constant which then turns into a combination of the second and the meter.

Making any of these measurements is difficult and requires a lot of fancy equipment, often involving lasers, vacuum chambers, electromagnets, and/or racks of electronics.  Here’s how NIST’s new F2 atomic clock works schematically and here’s a package from its inventor on the details.   As the F2 becomes a practical albeit sophisticated standard, even fancier methods are under development for the future.

The Kelvin, fundamental unit of temperature, is a nice exception to this complexity.  It is defined in relation to the triple point of water; that temperature at which the liquid, solid, and vapor phases of isotopically controlled, gas and contaminant-free water are in equilibrium.  Measure this and the Kelvin is 1/273.16 of that.   The aptly named triple point cell requires appropriate water, a skilled glassblower, and some patience.   Thermometers can be calibrated against this standard within and across laboratories.

The Fluke Corporation, despite its name, has long been a respected supplier of a wide variety of test and measurement equipment and they sell such a triple point cell.  In the right hands, it can allow the temperature of 0.01C (the Centigrade and Kelvin are equivalent) to be measured with an uncertainty better than ± 0.0001 °C.  Here’s Fluke’s Matt Newman showing how it is done and not a laser to be seen.

Addendum 20 February 2019: The Kelvin has also been redefined as of November 2018.  It is now tied to Boltzmann’s constant, k.  NIST says that not much will change for the moment since the triple point cell is a known, reliable tool.


All Up In Ya Grille: The Automobile Driving Museum

From back in the day when cars had teeth: An assortment of dental excellence from El Segundo’s marvelous Automobile Driving Museum.  It looks like a showcase of lovingly restored and superbly maintained American cars and it is all that.  And the side of fries?  Machines are meant to be used and on Sundays, they take a rotating subset onto the roads and let the public ride along.

I went in not knowing that the museum was actually closed for a private party but no one said anything and I browsed the collection at leisure.  When I go back – and I will – I look forward to opening doors, sitting in the seats, and enjoying the insides of these artefacts of a bygone era.  That’s also allowed and encouraged.

See more about the ADM through the two videos following the gallery.


Vimeo Channel: Rupert Hitzig

Whiffleball: Bill Hammack on the IBM Selectric

Integrated electronics make us forget about them.  Tiny packages with millions of transistors encapsulate so many functions so effectively that we don’t or can’t know what all they do.  This is a boon to manufacturers since repairing anything is all but impossible.  In the not-too-distant past, these functions or a small subset of them, had to be implemented in metal.  Techmoan does a stellar job of rediscovering old technology.  Prof. Bill Hammack of UIUC is also a master of this.  Here he explains how the whiffletree mechanism enabled the IBM Selectric typewriter to work its magic.  Beware – it is easy to lose a day watching his other videos and searching on the nuggets he finds.

Youtube Channel: Engineerguy