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start quite randomly and then, with experience, you define the
necessary intervals more accurately. There is the question of
subcontracting the calibration; it is not cheap regardless of whether
you do it yourself or subcontract it. It is our opinion that a
compromise can be considered. In fact, even though the metrology is
not the firm’s chief activity, it is a part of the “Management of
Quality”. If you retain part of it in the firm, it makes it possible to
maintain the user’s awareness of the importance of the measuring
instruments, of the notion of connected uncertainty, etc. However, a
firm cannot excel in everything and it must avoid spreading its
resources too thinly. It is always possible to ascertain whether there
are any local providers of services in metrology and, if so, their
charges.

The selection of standards
The content of this technical paragraph does not concern all firms;
the small- or medium-sized firms that do not use many standards
(merely a set of gauges or masses for example) need not worry. What
is presented here is a practically complete line of thought which can
reveal useful for the firms with a metrology service. However, let us
first recall the definition of the word “standard” in the “International
Vocabulary of basic and general terms in Metrology” (ISO document,
1993):
Standard: “material measure, measuring instrument or measuring
system intended to define, realize, conserve or reproduce a unit or
several known values of a quantity to transmit them by comparison to
other measuring instruments.”
Examples: 1 kg mass standard
100 ohm standard resistor
standard ammeter
gauge block
For a given metrological quantity, the standard will be the
“reference” of the firm. The standards may, or may not, differ from
the usual measuring instruments. The standards of the lowest orders
often have the same shape as the standards of usual instruments. They
are selected according to their type and their individual characteristics.
Thus, they will have to be differentiated from the other usual
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