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(in Russian, izmeritel’naia tekhnika), a branch of science and technology that deals with methods and devices for obtaining, by experiment, data on the quantities that characterize the properties and states of production processes and of objects being studied. The second half of the 20th century has been characterized by the gradual recognition that measurement technology is not so much the “art” of measurement as a separate scientific discipline, with its own system of concepts and its own methods of analysis. However, the process of formation of measurement technology as a unified scientific discipline is not yet complete. In many industrially developed countries, despite the high technical level of instrument-making, measurement technology is considered to be more a sector of industry than a branch of science. In English, for example, there is not even an exact equivalent of the Russian term; one of the most widely used terms is “instrumentation,” which may be rendered in Russian as priboristika [from pribor, “instrument” or “device”].
Measurement technology has existed since remote antiquity. Several millennia before the Common Era, the development of barter led to the measurement of weight and the appearance of scales. Primitive measurement technology was also required for the division of land into plots (measurement of areas), for establishment of daily activities, and for the development of a calendar (measurement of time); in astronomical observations and navigation (measurement of angles and distances); and in construction (measurement of dimensions). Some highly accurate measurements were made in the course of scientific research in the classical era (for example, the angles of refraction of light were measured, and the arc of the earth’s meridian was determined). Until about the 15th century measurement technology was not separate from mathematics, which is attested by such names as “geometry” (the measurement of the earth), “trigonometry” (the measurement of triangles), and “three-dimensional space.” Medieval mathematical treatises often contained a simple enumeration of the rules for measuring areas and volumes. The mathematical idealization of the actual process of measurement was retained in a number of important mathematical concepts, from the irrational number to the integral.
In the 16th to 18th centuries the improvement of measurement technology progressed along with the vigorous development of physics, which—at that time based solely on experiments—relied completely on measurement technology. The improvement of clocks and the invention of the microscope, barometer, and thermometer, the first electrical measuring instruments, and other measuring devices that were used principally in scientific research date to this period. As early as the turn of the 17th century, the improvement of the accuracy of measurements contributed to revolutionary scientific discoveries. For example, the precise astronomical measurements of Tycho Brahe enabled J. Kepler to establish that the planets revolve in elliptical orbits. The most important scientists, among them Galileo, Newton, C. Huygens, and G. Rikhman, devised measuring instruments and developed the theory of measurements. Every physical phenomenon that was discovered was embodied in a corresponding device, which in turn helped to determine accurately the value of the quantity being investigated and to establish the laws of interaction among various quantities. The concept of temperature was developed gradually, and a temperature scale was devised.
At the end of the 18th and in the first half of the 19th centuries, the requirements for precision in the finishing of machine parts increased sharply as steam engines spread and machine building developed; this brought about the rapid development of industrial measurement technology. In this period instruments for determining dimensions were improved, gauging machines appeared, and calipers were introduced. In the 19th century the principles of the theory of measurement technology and metrology were established; the metric system, which ensures uniformity of measurements in science and production, came into use. The works of K. Gauss, who developed the method of least squares, the theory of random errors, and the absolute system of units (CGSE) and (together with W. Weber) set forth the principles of magnetic measurements, were of great importance for measurement technology. As a result of the development of thermal power engineering and the introduction of electric communications equipment and, later, of the first electric power unit, measurement methods and devices that previously had been used only in scientific studies began to be used in industry; thermal engineering and electric measurement devices appeared. At the turn of the 20th century mefrological institutions began to be founded in industrially developed countries. The Central Board of Weights and Measures, headed by D.I. Mendeleev, was organized in Russia in 1893.
The beginning of the 20th century heralded a new stage in the development of measurement technology: electric—and later electronic—equipment began to be used to measure mechanical, thermal, and optical quantities and for chemical analysis and prospecting (that is, for measurement of all quantities). Such new branches as radio measurement and spectrometry also appeared. The instrument-making industry took shape. A qualitative leap in the development of measurement technology took place after World War II (1939-45), when, along with such branches as automation and computer technology, measurement technology emerged as a branch of cybernetics concerned with the collection and processing of measurement data.
Measurements are a very important stage in the activity of researchers and experimenters in all branches of science and technology. Measuring devices are the basic equipment of scientific research institutes and laboratories, an integral part of the equipment of any manufacturing process, and the main payload of meteorological rockets, artificial earth satellites, and space stations.
Modern measuring equipment is intended not only to exert an influence on human sense organs—as, for example, in the case of warning devices or reading of the results of measurement by an observer—but also, increasingly frequently, for automatic recording and mathematical processing of the results of measurements and for their transmission over a distance or for automatic control of processes. Mechanical, electrical, pneumatic, hydraulic, optical, and acoustic signals, as well as amplitude, frequency, and phase modulation, are used in devices and systems in various sections of measuring channels. Pulse and digital devices and servomechanisms are used very widely.
The process of measurement with modern measuring devices consists in the purposeful conversion of the quantity being measured into the most convenient form for a specific use (perception) by man or machine. For example, the importance of the operation of all electrical measuring instruments (such as ammeters, voltmeters, and galvanometers) is that by using them the electrical quantity being measured—changes in which cannot be directly assessed quantitatively by the human sense organs—is converted into a specific mechanical displacement of an indicator (a pointer or beam of light). This is also the function of many mechanical measuring devices and measuring transducers, by means of which various physical quantities are converted into a mechanical displacement (such as calipers, micrometer, spring balance, mercury thermometer, spring manometer or barometer, and hair hygrometer).
The development of measurement technology at the end of the first half of the 20th century showed that the conversion of measured quantities, the result of which is represented as an electrical quantity (such as current, voltage, frequency, or pulse duration), rather than as a mechanical displacement, is most convenient. Standard electrical equipment can then be used for all subsequent operations (transmission, recording, and mathematical processing of the results of measurement and their use in automatic control systems). The primary advantages of using the electrical methods of measurement technology are the ease of control of sensitivity, the low inertia of electrical devices, the possibility of simultaneous measurement of many quantities of different nature, and the convenience of assembling control machines and information measuring systems from standard units. The use of electrical measuring devices makes possible the measurement of processes that change both slowly and very quickly and the transmission of the results of measurements over great distances or their conversion into signals for controlling the processes being monitored. This is of great practical importance for both industry and scientific research.
There are a number of trends in modern measurement technology in terms of the fields of application of instruments and the types of quantities being measured: linear and angular measurements; mechanical, optical, acoustic, thermophysical, and physicochemical measurements; electrical and magnetic measurements; radio measurements; measurements of frequency and time; and measurements of radiation. Within each branch of measurement technology there are many separate methods of measuring physical quantities (which, in addition, differ in the measurement of quantities of various orders; thus, distances of 10-9m, 10-3m, 103m, and 109m are measured by entirely different methods). Therefore, the individual branches of measurement technology are rather weakly interconnected. In addition, smaller subdivisions for individual measured quantities continually arise within each branch—for example, tensometry (measurements of mechanical stresses on the surface of parts), vibrometry (measurements of vibration displacement, rate, and acceleration and of the frequency and spectral composition of vibration), and conductometry (measurement of the composition of solutions by their electrical conductivity).
Branches of measurement technology that differ in their particular approach to the process of measurement or in the purpose of measurement exist separately. For example, telemetry (measurement at a distance) contains radiotelemetry, which includes space radiotelemetry; measurements of the characteristics of random processes, including amplitude distributions, correlation-functions, power spectra, and electrical measurements of nonelectrical quantities; and digital measurement technology, which includes analog-digital conversion for feeding the measurement data into a computer. In addition to the trend toward further subdivision of measurement technology, an opposite trend—the consolidation of various branches of measurement technology on the basis of the community of initial positions, principles of construction, and block diagrams of equipment, and recently also on the basis of the community of the measuring equipment used—also exists. In the Soviet Union the State System of Industrial Devices and Automation Equipment and the Unitized System of Electrical Measuring Equipment have become an embodiment of this unification.
The need for measuring equipment is so great and diverse that, in addition to general instrument-making, such branches as aviation, analytical, geophysical, and medical instrument-making also exist. The study of the principles of measurement technology is part of the curriculum of virtually all technical higher educational institutions in the USSR; a number of polytechnic institutions and higher educational institutions of power engineering train specialists in data and measurement technology.
By the early 1970’s the trends of development of measurement technology had become very clearly defined. The most important of them in all fields were (1) a sharp improvement in the quality of instruments—reduction of errors to 0.01 percent or less, an increase in speed to thousands and even millions of measurements per second, improvement of the reliability of instruments, and reduction of their size; (2) expansion of the field of application of measuring equipment to include the measurement of quantities that previously were not measurable, and also toward more rigorous conditions for instrument operation; (3) universal conversion to digital methods not only in the measurement of electrical quantities but also in other areas (digital thermometers, manometers, gas analyzers, vibrometers, and other devices already exist), with the use and continuing improvement of analog devices; (4) further development of the systems approach to standardization of measuring equipment; and (5) extensive introduction into all measuring equipment of the methods of logical and mathematical processing of measurement data.
In metrology, particular note should be taken of the trend toward the conversion from man-made standards to natural standards based on the wave and discrete properties of matter. The unit of length is reproduced by means of the length of a light wave; the unit of time, by means of the period of oscillation of a natural radiator. Similarly, the unit of electric charge can be established in terms of the charge of the electron, the unit of mass in terms of the mass of one of the elementary particles, and so on. Methods of measurement that previously were considered to be of strictly laboratory or even metrological application, such as automatic interferometers with digital readout for measurements of small displacements, are finding broad industrial application in instrument-making. The miniaturization and microminiaturization of measuring equipment by means of the latest scientific achievements, in particular those of solid-state physics, is a very important trend in instrument-making.
Formulation of the general theoretical principles of measurement technology is an urgent task. The difficulty in developing them consists in the fact that the theory of measurement technology borders on complex problems of epistemology and mathematics.
In the USSR the following all-Union journals are published regularly: Izmeritel’naia tekhnika (Measurement Techniques; since 1939), Pribory i sistemy upravleniia (Control Devices and Systems; since 1956), Avtometriia (Autometry; since 1965), and Pribory i tekhnika eksperimenta (Instruments and Experimental Techniques; since 1956); the journal of abstracts Metrologiia i izmeritel’naia tekhnika (Metrology and Measurement Techniques; since 1963); Kontrol’no-izmeritel’naia tekhnika (Control and Measurement Techniques; since 1958); and Entsiklopediia izmerenii, kontrolia i avtomatizatsii (Encyclopedia of Measurements, Control, and Automation; since 1962). Monographs, handbooks, and booklets both in specific fields and on general problems of measurement technology and instrument-making are also published.
Foreign periodicals devoted to the problems of measurement technology include Archiv für technisches Messen (Munich, since 1931) in the Federal Republic of Germany; Messen. Steuern. Regeln (Berlin, since 1958) and Feingerätetechnik (Berlin, since 1952) in the German Democratic Republic; Instruments and Control Systems (Pittsburgh, since 1928), Journal of the Instrument Society of America (Pittsburgh, since 1946), Review of Scientific Instruments (New York, since 1930), and IEEE Transactions: Instrumentation and Measurement (New York, since 1952) in the USA; and Mérés és automatika (Budapest, since 1953) in the Hungarian People’s Republic.
REFERENCESMalikov, M.F. Osnovy metrologii, part 1. Moscow, 1949.
Arutiunov, V.O. Elektricheskie izmeritel’nye pribory i izmereniia. Moscow-Leningrad, 1958.
Kurs elektricheskikh izmerenii, parts 1-2. Edited by V.T. Prytkov and A.V. Talitskii. Moscow-Leningrad, 1960.
Ostrovskii, L.A. Osnovy obshchei teorii elektroizmeritel’nykh ustroistv. Moscow-Leningrad, 1965.
Turichin, A.M. Elektricheskie izmereniia neelektricheskikh velichin, 4th ed. Moscow-Leningrad, 1966.
Novitskii, P.V. Osnovy informatsionnoi teorii izmeritel’nykh ustroistv. Leningrad, 1968.
P. V. NOVITSKII and V. G. KNORRING