Ralph Gillmann asked in UDMA 25906:
What non-metric systems of units have been used in science or
engineering? I mean real systems, not hodge-podge collections of
units. Where are these systems documented? I've seen references to
the following:
British Absolute System
British Gravitational System
English Engineering System
Foot-Pound System
Inch-Pound System
But there is very little information about what these "systems" are.
In trying to promote the specification of SI in standards, I've made
the point that if non-SI units are used, then a standard document
should be referenced which defines the system and its use. Since
such documents don't seem to exist, I then want to make the point
that an engineering system of units needs to be specified, not just
a vague term such as "inch-pound units."
Ralph Gillmann
Federal Highway Administration
The British Absolute System was used by physicists. Its unit of mass
was the pound and its unit of force was the poundal = pound-force /
32.2.
The British Gravitational System was really two system. Mechanical
engineers used the pound-force and the pound-mass. In this system
pounds-force = pounds-mass x acceleration / g.
The aeronautical engineers used the pound-force and the slug-mass =
32.2 pounds-mass.
Civil engineers used the foot as their unit of length, while
mechanical engineers used the inch as their unit of length.
The metric system followed a similar evolution. In 1832 K. F. Gauss
proposed that the electric units should be based on the millinetre,
milligram and second. In 1873 to the British Association for the
Advancement of Science proposed elctrical units based on the
centimetre, gram and second. The first Congr�s International
d'Electricit� in 1881 adopted this system and named it the CGS System
(cenitmetre-gram-second). In France the MTS (metre-tonne-second)
system was legal from 1919 to 1961. Engineers also used the
metre-kilogram(force)-second system.
In 1901 the Italian engineer Giovanni Giorgi propoed a system based
on the metre, kilogram and second and an elctrical unit to be chosen.
This system was adopted in 1935 by the Commission Electrotechnique
Internationale. The amp�re was selected in 1950 as the 4th unit. The
Giorgi system was adopted by the Conf�rence G�n�rale des Poids et
Mesure in 1948, and, with the addition of other units in 1960 was
named the "Syst�me International d'Unit�s" designated as "SI" in all
languages.
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
