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– to know and control the environmental conditions as well as the
influence quantities which should be taken into consideration.
These environmental conditions are of differing natures;
depending on the measurements required they can be:
– the average temperature and its variations as a function of time and
space;
– the atmospheric pressure;
– the relative humidity of the ambient air;
– the quality of the air, the dust and the drafts;
– the shocks and the vibrations;
– the various fluctuations related to the supplies (power, fluids, etc.);
– the radioelectric disruptions.
These main parameters cannot be completely controlled and kept
independent from the outside environment, so they will have to be
maintained within certain limits (defined in accordance with
contractual demands). Thus, the user determines on the uncertainty on
the measurement results that is sought.
The requirements about premises depend on:
– the physical parameters (for example, thick lead walls and remote
controls are necessary for the measurements of ionizing radiations);
– the uncertainties (for example, in the national metrology
laboratories, the calibrations of gauge blocks are taken with
interferometers whose temperature is known within a few hundredths
of a degree Celsius; for the measurements of components with
margins of a few hundredths of a millimeter, variations of a few
degrees in the workshop will be acceptable).

III Answer the questions:
1 What kind of processes are used to carry out the operations of
measurement successfully?
2 What environmental conditions should be taken into consideration?
3 What do the requirements about premises depend on?

IV Fill in the blanks with appropriate words:
1 For equipment which requires periodical …, 1 parameters
some instructions must indicate how to deal 2 environmental
with this … . 3 limits
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