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– by studying the registers (monitoring cards, etc.) containing the
detailed information about the standard.
Note 3: the metrological reliability is the ability of a standard to
fulfill its expected function while maintaining the required freedom
from bias and repeatability during a predetermined period of time and
in set conditions.
Besides these basic characteristics, other metrological
characteristics can be important in certain cases, for example:
– measuring range or nominal value, total or partial, in the case of a
material measure;
– reference conditions;
– reading security;
– sensitivity;
– linearity or maximum permissible error of reversibility (hysteresis);
– dynamic metrological characteristics, etc.
The technical aspects are about:
– ease of use, simplicity and reliability of the standard;
– ease of transport, of taking to pieces and putting together again, of
installation, of connection and of setting up in the calibration or
verification device;
– protection against deterioration, pollution, interferences, etc. either
when the standard is being used or when it is just being preserved;
– special accessories necessary for the utilization or the preservation
of the standard (installation, reading, recording, electric power, etc.).
The economic aspects are about:
– the price of the standard and its accessories;
– the cost and the interval of the calibrations (including the costs
resulting from non-availability) during the calibrations;
– the cost of its utilization, its maintenance and its preservation;
– the possibilities of repairing, and the lifespan;
– the qualification of the personnel needed.
If you consider the restrictions imposed by the prescribed
metrological characteristics, selecting a standard can be regarded as
the pursuit of an optimum solution. Yet, in practice, there are even
other restraining factors, for example:
– the order of standardization of the equipment;

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