2.2 Physical-metrological fundamentals of constructing the RUTS systemsthe RUTS systems
2.2.2 Analysis of the state of the issue and the choice of the direction for
2.2.2.2 Brief review of papers on the theory of the construction of RUTS
The first attempt of a theoretical consideration of the RUTS system construction prob- lem was made by Prof. M. F. Malikov in his classical monograph [323] in the 1940s.
In this monograph Prof. Malikov tried to link a number of working standard ranks between primary measurement standards and working measuring instruments with a ratio of the accuracies of a verified and verifying measuring instruments, reasoning from the condition that an error of a verifying measuring instrument does not influ- ence the accuracy of a verified measuring instrument (“lack of influence” condition), i.e., on the basis of a so-called “criterion of a negligible error”.
In the same work an issue concerning the error accumulation in transferring the unit size from a measurement standard is examined. Among other requirements for constructing RUTS systems, only those are indicated according to which these systems have to be “on the level of contemporary achievements of measurement technique” and
“useful”, i.e., they should not complicate the verification procedure when there is no need to do this; moreover the elements and measures which these system contain have to provide a required accuracy in verifying working measuring instruments.
Further on, it is also noted that the construction of verification schemes is realized top-down, i.e., from a primary measurement standard. An analysis of the ratio of work- ing measurement standard and verified measuring instrument errors are examined in the first foreign works [153, 551] on the influence of verification schemes.
An interesting approach in the examination of RUTS systems (the authors call them
“metrological circuits”) is described by V. N. Sretenskiy and others. This approach is based on the investigation of the influence of metrological circuits on external systems (measurement technique, science, industry, nonmanufacturing business) and links gen- eralized parameters of these external circuits to the parameters of metrological circuits through general equations of external system operation efficiency. Unfortunately, did not receive proper attention, and the suggested approach was not developed.
Another approach to grounding and choosing a reserve of accuracy between the lev- els of a verification scheme was first suggested by N. A. Borodachev in his monograph [63].
In this monograph the author proceeds from considering the verification defect, i.e., he considers verification to be one of various kinds of technical controls for product parameters (compliance of product parameters with their requirements).
Between 1958 and 1974 a great number of theoretical works were devoted to the examination of this approach. Among them are E. F. Dolinskiy [140, 141], A. N. Kar- tasheva [254], and K. A. Reznik [400–402].
Section 2.2 Physical-metrological fundamentals of constructing the RUTS systems 99 These works deal with only one form of verification, i.e., the control of metrological success of a measuring instrument (fit–unfit) and, strictly speaking, are not related to the problem of transferring the unit size. However these works stimulated the solution of the problem of constructing verification schemes. In practice this trend of inves- tigations corresponded to the solution of the task of selecting reference measuring instruments for the verification of working measuring instruments. The first review on works of this type was collected in 1975 by A. V. Kramov and A. L. Semeniuk [279].
Subsequently this trend evolved into the problem of the “quality of verification”:
N. N. Vostroknutov, M. A. Zemel’man, and V. M. Kashlakov [255, 538].
The first attempts to introduce the “collective” parameters of verification schemes into consideration, with the purpose of optimizing these systems, were made by N. A. Rubichev and V. D. Frumkin [414], and E. L. Crow [132].
The task of optimizing the structure of a verification system was solved reasoning from the criterion of its minimum cost by the method of undefined Lagrange multi- pliers. In the first of these, the following initial parameters of calculation were chosen:
the number of working measuring instruments to be verified, verification time and the working measurement standard of the lowest category, the verification (calibration) interval, the error of a working standard of the lowest category, and the costs of real- ization and maintenance of a verification system.
The results in question for solving the problem were: the total number of categories, the number of working standards in each category and error ratio for working stan- dards between the categories. However, calculations have shown that the function of verification system costs turns out to be weakly sensitive to the ratios of measuring instrument errors between the categories of the verification system as well as to the law of accumulating errors (an arithmetic or quadratic error), i.e., the minimum of the cost function appears to be rather “blunt”.
Moreover, it was noticed that there was no sufficiently reliable input data, especially of an economical character. Similar tasks were solved in other works: L. G. Rosengren [409]; V. E. Wiener and F. M. Cretu [544].
In the paper written by S. A. Kravchenko [282] a calculation of a concrete verifi- cation system in the field of phase measurements is realized. The author, using infor- mation about the costs of developing and manufacturing the phase measuring setups of different accuracies, makes an attempt to optimize both the number of verification scheme levels and the ratio of working measurement standard accuracies between sep- arate levels.
A further development in investigation of an optimal construction of the system of transferring the unit sizes followed the path either by detailing separate aspects of the system structure and the process of its operation or by using new methods of problem solution.
K. A. Reznik in [401] sums up the results of his long-term investigations on deter- mination of a number of verification system steps on the basis of the productivity and verification intervals of measuring instruments on each level, as well as a joint park
of working measuring instruments (the maximum possible number of steps) with a detailed study of the influence of a kind of distributions of the corresponding errors.
The results of these works were used as a basis of the normative document MI 83–76 [331].
In A. M. Shilov’s work [435] the problems of accumulating in a verification scheme the errors which change with time as well as those of a relationship between errors of a reference measure and a verified one (a working measure) are taken into account. It is claimed that the approach suggested demands significantly less a priori information than the approach based on the probability of a verification defect.
V. P. Petrov and Yu. V. Riasniy in [380] analyze a method of constructing optimal verification schemes according to the criterion of a minimum of economical costs, however taking into account the probabilities of verification defects. As the initial parameters of the task, the operation costs dependencies of measuring instruments, disposable for service and unworkable, on their errors, as well as the losses due to operation of unworkable measuring instruments, are superinduced.
In a series of works by A. I. Vasil’ev, B. P. Zelentsov, A. A. Tsibina, A. M. Shilov N. G. Nizovkina [435, 525–527, 532, 533] from the city of Novosibirsk, great attention is given to investigating the role of and determining the verification interval values for working and reference measuring instruments, as well investigating the influence of verification defects on metrological reliability of measuring instruments, the calcula- tion of parameters and modeling of a system of transferring the unit size and, finally, the problems of a system approach to the assurance of measurement uniformity.
It is also proposed to use verification intervals as variable parameters, with the help of which it is possible to control the uniformity of measurement (or, more precisely, to control the uniformity of measuring instruments). Moreover, the system for ensur- ing the uniformity of measurements in a country (which the authors identify in its sense with the system of transferring the unit sizes) is represented in the form of two interconnected subsystems, one which supplies metrological service bodies with ver- ification equipment, and another which provides the uniformity of applied measuring instruments. Factors influencing the structure and operation of the system for ensuring the uniformity of measurements are determined:
(1) errors of measuring instruments and methods of verification on all levels of a verification scheme;
(2) normalized metrological characteristics of measuring instruments;
(3) availability of standardized procedures of carrying out measurements and verifi- cations;
(4) quality of verifications (on distribution of errors and probabilities of verification defects);
(5) number of verification scheme steps;
Section 2.2 Physical-metrological fundamentals of constructing the RUTS systems 101 (6) nomenclature and park of measuring instruments throughout the steps of a veri-
fication scheme;
(7) metrological state of measurement standards and working measuring instruments;
(8) coefficients of their usage;
(9) productivity of measurement standards;
(10) distribution of measuring instruments over the territory and a need of its trans- portation for verification;
(11) need for verifications in situ;
(12) full strength of metrological bodies with verification equipment;
(13) periodicity of measuring instrument verification;
(14) prices of measurement standards, verifications, operation costs;
(15) losses due to disfunction of measurement uniformity;
(16) losses due to the retirement of measurement standards and measuring instruments for verification and repair;
(17) limitation of resources for metrological assurance.
In these works an attempt is made to give definitions for the concepts “measurement uniformity assurance” and “uniformity of measuring instruments”, as well as some properties of a system for ensuring measurement uniformity as a complicated cyber- netic system are pointed out.
L. A. Semenov and N. P. Ushakov’s work [431] is devoted to the problem of reduc- ing the costs connected with the arrangement and function of a network of verification bodies at the expense of their rational disposition. The authors carry out an analysis of an economic-mathematical model of the problem concerning integer-valued linear programming for given sets of the they types of working measuring instruments and their parks, points of working measuring instruments and working measurement stan- dards dislocation, verification intervals, taking into account the costs of verification and transportation of measuring instruments.
A brief review of the methods and theory of mass service in determining the need for verification means (including problems of optimal disposition of verification equip- ment) is given by V. V. Belyakov and L. N. Zakashanskiy [50].
In Ya. A. Krimshtein’s work [283] the problem of the synthesis of an optimal struc- ture of a metrological network (according to the criterion of a total cost minimum) for transferring the unit size to the park of working measuring instruments of one group.
In contrast to [431], here there were chosen not only versions of disposals of the ref- erence measuring instruments realizing the verification of working measuring instru- ments, but the structure of the whole verification network. Optimal parameters of the problem are determined by methods of integer-valued measurement programming.
In a series of works by specialists from the Tomsk Politechnical Institute, which are summarized by A. I. Kanunov, T. V. Kondakova, E. P. Ruzaev, and E. I. Tsimbalist
[252], it is suggested to solve the synthesis problem of optimal structures of verifica- tion schemes by way of a formalized description using graph theory. At the same time sets of working measurement standards and working measuring instruments are rep- resented in the form of peaks, and links between them are shown in the form of graph ribs. Due to a lack of links between the elements of one level in a considered multi- level hierarchical system, its optimization can be performed step by step rising from the bottom levels to the upper ones and having an algorithm of optimization within the adjacent levels.
In the work of G. V. Isakov [229] attention is paid to the complexity of a real sys- tem of transferring the unit sizes and to the need for solving the problems relating not only to the structure of methods and means for transferring the unit sizes, but to executive routine support components (including organizational, trained, financial, in- formationa,l and lawful ones).
In L. A. Semenov’s work [428] an idea for a new approach to optimization of the unit size transfer system is expressed for the first time, according to which it is necessary to consider the interconnection of three systems: the system of the unit reproduction (throughout the totality of quantities measured), proper systems of the unit size transfer (for separate quantities), and a system of information consumption (all sections of the economy of a country). The first and third systems impose limitations from the “top”
and “bottom” onto the second one.
Taking this into account, the optimization of the unit size transfer system is sug- gested to be carried out stepwise: at the first stage it is necessary to determine a number of steps and characteristics of the unit size transfer system (construction of a verifica- tion scheme); at the second stage the optimization of the disposal of reference measur- ing instruments (the system structure) is realized on the basis of economical criteria.
Moreover, some issues of the increase in error in transferring the unit size from a mea- surement standard to a working measuring instrument are considered, particularly in finding new graduation characteristics of a verified measuring instrument.
In T. N. Siraya’s work [442] errors of unit size transfer from a group measurement standard, as well as errors of unit reproduction and maintenance by a group standard are considered.
One more approach to the problem of optimizing a system of the unit size transfer by an economical criterion is given in [499] by V. S. Svintsov This work is a total of all his previous studies. It is based on the fact that the periodicity of verification (veri- fication interval) simultaneously influences the quality of verification and the amount of losses because of the use of damaged working measuring instruments (with a latent metrological failure), i.e., a variable parameter is the verification interval. Thereby the above-mentioned idea in L. A. Semenov’s work [428] is partially realized.
However the author acknowledges that to use the approach he suggests is difficult in practice, because a great amount of initial data of a technical and economical char- acter is required. In the next work by the same author [500] a model of an operation process is described which was designed to perform, in principle, “optimization of
Section 2.2 Physical-metrological fundamentals of constructing the RUTS systems 103 metrological maintenance of measuring instruments not only in accordance with the periodicity of verification but also simultaneously in accordance with the duration of their previous no-failure operation”.
The paper written by V. A. Dolgov, V. A. Krivov, A. N. Ol’hovskiy, and A. A. Gris- hanov [139] and that by A. A. Avakyan [28] are also of interest, although they are not directly related to the problem of optimizing the park and nomenclature of working measuring instruments and the methods of measurements, which, certainly, influences input parameters of the system considered.
An original approach to the analysis and synthesis of verification schemes, which is based on applying the theory-group methods, was proposed by V. A. Ivanov in [239].
But in fact, the practical use of this approach now seems rather unclear.
Finally, in the work by O. A. Kudriavtsev, L. A. Semenov, and A. E. Fridman [286]
an attempt is made to classify the main problems of constructing a system for ensuring the uniformity of measurements, which yield to mathematic modeling (including the problems concerning the RUTS systems). However, due to the fuzziness of the signs chosen, the classification given cannot be seen as a successful one.
The classification of the efficiency indices of the separate elements of the system appears to be insufficiently complete, clear, and grounded. More interesting is an at- tempt to develop a general model of a system based on a synthesis of the existing ideas about it. However the requirements for the model stated in the work are also insuffi- ciently grounded, and the problem of formalization itself in a general form (through a minimum of the efficiency criterion, which appears to be proportional to a number of working measuring instruments) is simply wrong.
Thus, even this brief review of published works (we tried to select the most “central”
ones) shows that at present there have been a significantly large number of theoretical investigations on various problems connected with constructing the RUTS systems in separate kinds of measurements (see, for example [501]). Unfortunately, among all these works there is nothing on constructing a system for reproducing the units (i.e., the interspecific construction of a general RUTS system). References concerning this problem are given in the respective paragraphs of this chapter.