Analysis of methods and types of measurements in qualimetry

In the framework of the Fourth Industrial Revolution Industry – “Industry 4.0”, metrology becomes an integral part of the production process, the characteristic feature of which is the development and merger of automated production, data exchange and manufacturing technology into a single self-regulated a system with the least or no human intervention in the production process. Measurement, testing and quality control will no longer be considered as a parallel procedure, but rather an integral part of the manufacturing process. Accordingly, the functions of metrology and the scope of its study of metrology are substantially expanding. One of the new areas of research in modern metrology is qualimetry – the scientific field, the subject of study of which is the quantitative assessment of product quality. Today in qualimetry due to the specificity of the object of research –
production – there are a number of unresolved theoretical and methodological problems. In particular, it is a problem of ensuring unity and metrological traceability of the results of product quality assessment and analyzing the accuracy and reliability of the product quality estimates obtained. Solving these problems, according to the authors, is possible only in a complex combination of the methodology of metrology and qualimetry. Metrology, the science of measurement and its application, has the strong scientific, practical and legal tools, which allows research in any field of knowledge. Analysis of the ways of solving these problems is the subject of this study. First of all, the analysis of the difference between the key concepts of metrology and qualimetry – “measurement” and “evaluation” are developed. Measurements in their essence provide for a comparison of the measured value with the measure, as well as a description of the measured value in accordance with the intended use of the measurement result, measurement procedure and a calibrated measuring system functioning in accordance with the regulated measurement methodology and taking into account the measurement conditions. Consequently, the notion of "measurement" is directly related to such concepts as the result of measurement, measurement unity, accuracy of measurements, metrological traceability of measurement results and other key concepts of metrology. That allows comparing the results of measurements of characteristics of identical objects obtained in different laboratories, different methods and means in different conditions, as well as to implement the condition of metrological traceability of measurement results. The above signs of the notion of “measurement” are not at all inherent in the con studying the quality of products can not objectively compare the results of research on the quality of identical products obtained in different laboratories, different methods and means, in different conditions and carry out metrological traceability of the results of product quality assessment, which, of course, significantly reduces the possibilities qualimetry regarding the objectivity and reliability of the obtained product quality assessments. From the standpoint of modern development of world metrology, types of measurable quantities in qualimetry and methods of their measurement are considered. As can be seen from the analysis of current NDs] and literary sources, the numerical estimates of product quality are single absolute quality indices Рі that are equal to the corresponding properties of the products under study рі ,i =1,2,¼,п , single relative quality indexes Kі , as well as integrated indexes of product quality and product quality level. They are the main measurable values in qualimetry. In order to effectively combine the methodology of qualimetry and metrology in the field of qualimetry, it is advisable to use the basic measurement methods and the main provisions of the reprezentative theory of measurement. Method of measurement – a general description of the logical sequence of operations in the measurement. The basis of any measurement is the comparison of the measured value with the measure that stores and reproduces the unit of this value. Consequently, the measure of measurable value is always present in the measurement process, but its presence and methods of use are manifested differently, which underlies the classification of measurement methods. Therefore, it is advisable to classify the measurement methods according to the following features:
• by the way of using the measure;
• by the way of comparison with measure;
• by the completeness of comparison with the measure.
By the way of using the measure, all measurement methods are divided into two groups:
• measurement methods of time-consuming or implicit comparison with the measure;
• measurement methods of simultaneous or direct, explicit comparison with the measure.
Methods of time comparison with the measure or, as they are called, direct measurement methods are based on the use of measuring instruments whose scales are calibrated in units of measured values. Methods of simultaneous or direct comparison with the measure are based on the use of the measure of the measured value directly in the process of measurement, that is, the comparison of the measured value with the magnitude reproduced by measure is carried out in each concrete measurement. 
Comparison methods, in turn, are divided into the following types:
• by the way of comparison with measure: substitution method of measurement, opposition method of measurement, compensation method of measurement, complementary method of measurement, coincidence method of measurement, resonance method of measurement;
• by the completeness of comparison with the measure: null method of measurement, differential method of measurement.
According to the general classification of measurements in qualimetry, as well as in general in metrology, there is possible to use the following types of measurements:
• direct measurements;
• indirect measurements – mediated (indirect) measurements, aggregate (indirect) measurements, compatible measurements.
The model equations of the two main types of measurements in qualimetry and the corresponding systematic errors, which find the uncertainty (uncertainty) of the results of measurements of product quality characteristics, are given in the table below. (Note: The formulas given in the table correspond to measurements with one-time observations). Effective using of all theoretical, practical, legislative and scientific foundations of modern metrology in the field of qualimetry, in particular, measurement methods, measurement methods and methods for measuring the accuracy of measurement results taking into account the specificity of the research object – the product – requires further analysis and research.