Lecture 3 The Basics of metrological support. Scientific bases of metrological support. Organizational basis of metrological support.

Concepts of unity and accuracy of measurements" are defining for theoretical metrology and metrological practice. Distinction and at the same time interrelation, interconditionality of these concepts define character, the contents, an orientation and forms of the organization of metrological providing any and production problems.

Possibility of application of results of measurements for the correct and effective solution of any measuring task is defined by the following three conditions:

1. results of measurements are expressed in the established units and (or) forms;

2. values of indicators of accuracy of these results are known (with the necessary set reliability);

3. values of indicators of accuracy provide optimum (according to the chosen criteria of an optimality) the solution of a task for which these results are intended.

If results of measurements meet the first two conditions, everything is known of them that it is necessary to know for adoption of the reasonable decision on possibility of their use. Such results can be compared. They can be used in various combinations, various people and the organizations. In this case it is possible to tell that the unity of measurements, i.e. such condition of measurements at which their results are expressed in the established units and (or) forms and an error of measurements is provided are known with the set probability.

If results of measurements do not possess any of these properties i.e. their accuracy is unknown or incorrectly determined, results of measurements, actually unsuitable for the solution of these or those measuring tasks, can be mistakenly taken for the suitable. Such results cannot be compared or shared. In these cases it is accepted to speak about absence of unity of measurements.

The third of the listed above conditions defines specific requirements to accuracy of the applied methods and measuring instruments.

Search of rational forms and methods of ensuring unity of measurements is conducted long ago. So, at the end 60-h-the beginning of the 70th the basic principles and provisions of ensuring unity of measurements were developed, the complex of the state standards regulating these principles and provisions within the State system of ensuring unity of measurements (GSI) is created.

Basis of this system was two situation "prompted" by measuring practice.

1. Accuracy of results of technical measurements can be reliable it is estimated only on the basis of the preliminary analysis of the possible reasons and is tochnik of errors of measurements and aprioristic assessment of these values pog reshnost. After results of measurements are received, to estimate them real accuracy it is not possible.

Therefore, for ensuring unity of measurements it is necessary to create and regulate such rules of preparation and carrying out measurements, processings and registrations of their results which observance guarantees a certain accuracy of all of the measurements which are carried out by these rules.

2. Before creation and introduction of GSI by the main and in essence measuring instruments (measures and measuring devices) were the only object of activity of metrological service. However the real accuracy of technical measurements was increasingly caused not by the tool, but methodical errors connected with introduction of indirect methods of measurements, toughening of conditions of use of devices, dynamic properties of objects of measurements, etc.

Therefore, ensuring unity of measurements required inclusion in a field of activity of metrological service of processes and results of measurements. Thus the traditional tasks connected with ensuring uniformity of measuring instruments entered a complex of tasks of ensuring unity of measurements which includes establishment and development:

units of the measured sizes (parameters) allowed to application;

methods and means of reproduction and storage of the sizes of units of the measured sizes (parameters);

methods and transmission media of the sizes of units from standards to working measuring instruments;

test methods and checking of measuring instruments;

nomenclatures, principles of rationing, assessment and control of metrological characteristics of measuring instruments;

forms of expression of results and indicators of accuracy of measurements;

methods of calculation of indicators of accuracy of techniques of performance of measurements;

principles of certification of techniques of performance of measurements.

The general rules of the solution of the specified tasks and> were regulated by the GSI fundamental standards which in turn served as basis for development of a large number of the state and industry standards, other normative documents of GSI concretizing requirements, norms, rules of ensuring unity of measurements in relation to separate types and areas of measurements, types of measuring instruments to branch and production specifics of separate branches of a national economy.

It should be noted that practical activities according to the accuracy of results of measurements (being guided by the corresponding regulated rules) are carried out by groups of experts (technologists, designers, - operators) which plan and directly carry out measurements. Bodies of metrological service, solving the problems stated above, create necessary conditions (Gosstandart of the USSR and its organization — at the interindustry level; bodies of departmental metrological services — at the level of departments, the enterprises and the organizations) for the correct and uniform estimates of accuracy of the "made" and used measuring information. For realization of these conditions bodies of metrological service have to aim activity of departments, enterprises and organizations at providing unity of measurements (the analysis, forecasting, planning, an assessment and rationing), to control its results, to provide systematic increase of its efficiency and compliance to modern and perspective requirements of a national economy.

Thus, on the basis of achievements of metrological science rules of metrological preparation and performance of measurements, processings and registrations of their results are developed. Implementation of metrological rules which obligation is established by normative and technical documents GSI, provides the guaranteed accuracy of results of measurements. Full, high-quality and universal implementation of these rules is provided and controlled by bodies of metrological service. Control of activities for ensuring unity of measurements in country scales (at the interindustry level) is exercised by Gosstandart of the USSR and its organization.