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Supplement Reading

The traceability of the measurements
It has to be said repeatedly: the calibration requirements and the
traceability define the quality of the measurements. The metrological
function is responsible for the management of the quality of the
measurements. This has to be taken into consideration from the
beginning of the process that leads to the selection of the method of
measurement, and then the means of measurement.

The necessity of traceability of the measurements
Traceability is the very basis of metrology. What good is it to take
measurements if the measurements do not mean the same thing to
everybody? For example, let us look at the measurement of the value
th
of the “foot” in the past. Until about the 18 century (and even later),
the “foot” was used as a unit to measure distances.
Everyone used the same word. A worthy sample of this quantity
was available to avoid arguments, such as “is it a child’s foot, or a
woman’s, or a man’s?” The problem was that when the value was
translated into the metric system, it gave the following results:
– foot of the King of France 32.48 cm
– Roman foot 29.63 cm
– foot from Bordeaux (South of France) 35.70 cm
– foot from Lorraine (East of France) 28.60 cm
– foot from Vienna (Austria) 31.50 cm
These discrepancies resulted from the lack of a national reference
(let us not even talk of a European one), and of local comparisons to
each reference. Just imagine the Airbus today manufactured from all
parts of the world. It is therefore indispensable to have metrological
references in one’s firm and to have them compared to national
reference quantities by calibration. Comparisons between accredited
laboratories are made by national accreditation bodies (the COFRAC
in France, the Deutscher Kalibrierdienst (DKD) in Germany) and
there are programs of comparison that make it possible to ensure that
the standards of different countries are related. It is to be regretted that
all the industrialized countries are not at the same level of progress in

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