UDC 389.001

USING A PARAMETRIC APPROACH IN THE DESIGN OF METROLOGICAL COMPLEXES

M. S. ROITMAN, E. I. TSIMBALIST, E. N. RUZAEV

(Presented by the scientific seminar of the Department of Radio Engineering)

A brief analysis is given of the normative-technical documentation of the State System for Ensuring the Uniformity of Measurements. The shortcomings of the system of documents under an instrument-based approach to its construction are shown. The use of a parametric approach is proposed both in creating new normative documents and in designing reference measuring instruments. The advantages of such an approach are shown.

Illustrations 2, bibliography 2.

At present, the normative-technical documentation of the State System for Ensuring the Uniformity of Measurements (NTD SSI), in the form of GOST standards (instructions) and methodological guidelines (MG), presupposes the standardization of the basic technical parameters of working measuring instruments (WMI), as well as of the methods and means for their verification [1]. In addition, in order to ensure the uniformity of measuring instruments and measurement methods in the CMEA member countries, the Permanent Commission on Standardization has issued a number of recommendations on standardization (RS) in the field of metrology and, in particular, RS on electrical measurements [2].

An analysis of the NTD SSI shows that they have been compiled on the basis of the existing needs for the methods and means of measurement of existing WMI. The transfer of the reference values of each parameter is presented most clearly in RS, which contain verification schemes broken down by accuracy. However, the linking of the NTD SSI to existing instruments has a number of negative aspects. The appearance of new WMI having better metrological characteristics in comparison with existing ones, as a rule, inevitably leads to additions to, or revision of, the current GOST standard, instruction, or MG. As a result, up to 40% of existing WMI are currently not provided with verification, which leads to great difficulties both in the manufacture and in the operation of these instruments. This is a consequence of the “instrument-based” approach in the development of normative-technical documentation, when the methods and means of verification of a given type of instrument (for example, generators, voltmeters, electric-energy meters, etc.) are standardized.

On the other hand, in analyzing the input flow of WMI, it may be noted that, despite their large nomenclature, there is an immeasurably smaller number of controlled parameters. For example, in the field of electrical measurements the principal verified parameters of WMI are: voltage \(U\), current \(I\), electrical resistance \(R\), capacitance \(C\), inductance \(L\), frequency \(f\), phase \(\varphi\), transmission coefficient \(K\), nonlinear-distortion coefficient \(K_f\),

Let us note that combinations of controlled parameters make it possible to represent any RMI subject to verification. For example, \(f^{in}\) denotes a frequency meter, \(f^{out}\) a source of a signal of standard frequency, \((U_{\sim}, f)^{in}\) selective voltmeters, \((U_{\sim}, f, K_f)^{out}\) a generator of sinusoidal voltages, etc.*

Thus, the entire stock of RMI can be conditionally represented not as the sum of separate types of instruments and devices, but as a list of the basic electrical parameters and their combinations. Using such a parametric approach, one can compile a table of correspondences: electrical parameter—types of RMI instruments.**

Noting the commonality of the basic controlled parameters of RMI, it would be expedient to supplement the NTD of the SMI in the form of GOST standards on methods and means of control of an electrical parameter at specified values of the limits and with standardized errors.

In our opinion, these GOST standards should be fundamental in developing the NTD of the SMI for methods and means of verifying individual types of RMI.

Such documentation would presuppose standardization of methods and means of measuring an electrical parameter for any RMI for which this characteristic is controlled.

The development of such documentation would make it possible to:

1) reduce the number of GOST standards and MI;

2) unify the methods and, most importantly, the means of verification for any RMI, including newly designed ones. Unification would undoubtedly require a single developer of the documentation for a given parameter and would lead to a unified approach in its development;

3) provide, by means of unified documentation, all types of apparatus and instruments, including service equipment;

4) reduce the number of amendments and additions to NTD associated with the appearance of modified or new RMI;

5) extend the periods of validity of NTD, since methods and means of verification are longer-lived than RMI;

6) ensure a unified approach to the development of modules of verification equipment for a given parameter(s), its(their) limits and accuracy.

Elements of such an approach are present in normative-technical documentation, for example, in certain VS and GOST standards. Thus, in the “All-Union verification scheme for means of measuring alternating-current voltage at high frequencies” (GOST 8.075-73), among RMI we find oscillographs, electronic voltmeters of various types, measuring generators, i.e., precisely those instruments for which voltage is the controlled parameter. The same can be seen in the verification scheme for means of measuring electrical capacitance and in some others. Unfortunately, in other NTD we have a “Verification scheme for ammeters,” and not a “Verification scheme for means of measurement and sources of direct and alternating current,” etc.; the list of similar examples can be continued.

In implementing the parametric approach in the design of metrological laboratories, it is necessary to replace the existing standard measuring instruments (OSI) with modules, each of which implements one verified parameter of RMI. The modular construction of a laboratory will make it possible:

* The following notation is adopted here: \(in\)—the RMI measures the given parameter; \(out\)—the RMI is the “source” of the indicated parameter.

** Let us note that there may be formulated a combination of controlled parameters for which at present there is no corresponding RMI and for which NTD for means and methods of verification can be developed only after their appearance in verification practice.

1) sharply reduce the stock of MMI;
2) create unified modules suitable for use in various laboratories in which the given parameter is verified.

Let us consider what effect is achieved by introducing the modular construction of laboratories, using the example of a laboratory for radio-engineering measurements.

The input stream into this laboratory consists of the following MMM:

1) measuring generators:
a) low-frequency;
b) medium-frequency range;
c) high-frequency;
d) quartz frequencies;
2) electronic voltmeters:
a) direct current;
b) alternating current;
c) universal;
d) selective;
e) phase-sensitive;
3) measuring amplifiers;
4) electronic phase meters.

Thus, the stock of MMM comprises eleven types, without taking into account intratype modifications. On the other hand, in all these instruments only ten parameters are verified:

\[ U_{=}^{in},\ U_{\sim}^{in},\ U_{\sim}^{out},\ I_{=}^{in},\ I_{\sim}^{in},\ R^{in},\ f^{out},\ f^{in},\ K_f^{out},\ \varphi^{in}. \]

A radio-engineering measurements laboratory built on the basis of the current modern NTD of the SSM, and with the most modern reference apparatus selected, will comprise 25 units of reference equipment and a mass of auxiliary equipment (Fig. 1).

When the parametric principle of laboratory construction is used, the stock of MMI will comprise only nine modules:

\[ f^{in},\ U_{=}^{out},\ U_{\sim}^{out},\ U^{in?},\ I_{=}^{out},\ I_{\sim}^{out},\ R^{out},\ K_f^{in},\ \varphi^{out}. \qquad \text{(Fig. 2)} \]

In addition, to carry out verifications using these modules, no auxiliary equipment at all is required.

In addition to stationary metrological laboratories, mobile verification complexes are necessary for carrying out verifications at the locations of MMM.

A mobile complex must provide verification of almost all types of MMM as the corresponding stationary one does, but these MMM must have lower accuracies and narrower ranges of the parameter being verified. If the parameter-verification modules used in the stationary laboratory have a cellular structure, i.e., each module consists of several units, then, with corresponding unification of these units, they can also be used in creating modules for mobile complexes.

For example, the module \(I^{out}\) of a stationary laboratory consists of four cells:

\[ \text{No. }1\ I_{=}^{out}\quad D_I = 10^{-15} \div 10^{-6}\ a; \]

\[ \text{No. }2\ I_{=}^{out}\quad D_I = 10^{-6} \div 5\ a; \]

\[ \text{No. }3\ I^{out}\quad D_I = 5 \div 100\ a; \]

\[ \text{No. }4\ I_{\sim}^{out}\quad D_I = 100 \div 10000\ a. \]

Fig. 1. Structural scheme for selecting verification schemes for laboratory radio-engineering measuring instruments.

In the figure:

• Working measuring instruments
• Parameters of the WMI
• Samples of measuring instruments

Row labels:

1. Low-frequency measuring generators
2. Ultrahigh-frequency generators of medium frequencies
3. High-frequency measuring generators
4. Radio-frequency voltmeter B5-1
5. Phase-sensitive voltmeter B5-2
6. Selective voltmeters
7. Electronic voltmeters \(U_{=}\)
8. Electronic voltmeters \(U_{\sim}\)
9. Universal electronic voltmeters
10. Measuring amplifiers *
11. Measuring amplifiers **
12. Electronic phase meters

Instrument headings visible across the matrix:

\(S3\text{-}22\), \(V7\text{-}16\), \(V3\text{-}24\), \(S6\text{-}11\), \(V6\text{-}1\), \(V6\text{-}2\), \(S3\text{-}102\), \(F2\text{-}15\), \(V1\text{-}4\), \(V3\text{-}33\), \(ISO\text{-}5M\), \(D1\text{-}11\), \(G3\text{-}59\), \(D8\text{-}5\), \(R\text{-}4001\), \(G3\text{-}41\), \(R\text{-}4003\), \(M\text{-}1201\), \(M\text{-}1150\), \(D\text{-}566\), \(D\text{-}570\), \(E\text{-}34\text{-}4\), \(E\text{-}76\), \(SP6\), \(330\), \(M197\).

Parameter labels visible in the matrix include:

\(f_{\text{out}}\), \(U_{\text{out}}\), \(K_g\), \(U_{\sim}\), \(I_{=}\), \(I_{\sim}\), \(R\), \(\varphi\).

Legend:

▧ — one verification scheme
■ — several variants of verification schemes

For the module \(I_{=}^{out}\) of a mobile laboratory it is rational to use units No. 2 and No. 3, since the parameter being verified, \(I_{=}^{in}\), for this laboratory has a narrower range:

\[ \Delta I = 10^{-6} \div 100\ \text{A}. \]

Thus, having a set of unified cells, it is possible to assemble the corresponding modules both for stationary and for mobile laboratories, i.e., the need for additional

Fig. 2. Structure of a laboratory for radio-engineering measurements with the parametric approach

[[unclear: beginning of line clipped]] design and production of MSI for mobile complexes is eliminated. Thus, the fleet of MSI having the same functional purpose will be sharply reduced and will be assembled from unified cells.

Summarizing all of the above, it may be said that the parametric approach in the design of metrological complexes has major advantages and, in the future, will become the principal one in solving problems of metrological servicing.

LITERATURE

1. Series of GOST standards, “State System for Ensuring the Uniformity of Measurements.”
2. Series of “Recommendations on Standardization” for the CMEA member countries.