BASIC SOCIAL NEEDS Three general, ever present needs of our society have brought the national measurement system into being. In meeting these needs, the measurement system, working together with other social systems, enables society to accomplish national objectives such as space exploration, quality education, adequate defense, an improved standard of living, consumer welfare. The three needs are: (1) Basic measurements and standards.-The nationwide need for a complete and consistent system of physical measurement, properly coordinated with those of other nations, requires the ability to make accurate, reliable, precise, and compatible measurements in terms of a common language of units and methodology. (2) Matter-materials data and standards.-There is continuing need for a systematic and readily accessible body of accurate, reliable, precise, and consistent data on the properties of materials in different environments, and for information, reference materials, and conceptual knowledge that will make possible the effective use of such data. (3) Technological measurements and standards.-To an increasing extent, the economy has come to depend on exchange in the marketplace of products and services having a high technological content. This creates a need both for uniformity of product characteristics and for a language for stating user requirements in terms of the performance capabilities of products and standards. IMPORTANCE OF THE SYSTEM Estimates of activity within the U.S. measurement system include the measurements made every day by each person-ranging from the relatively crude ones of checking the time or temperature, reading the speedometer, or buying steak by the pound, to the highly sophisticated and often exquisitely complex measurements made in the laboratories of science and industry. Rough estimates indicate some 20 billion measurements are being made every day in this country. Industries that account for two-thirds of the gross national product invest about $14 billion a year in measurement and expend about 1.3 million man-years in the process. Some $25 billion is invested in measuring instruments and this investment is being increased by some $412 billion each year. In addition, some $20 billion is invested in research to provide measurement data and about $3 billion a year is being added to this amount. Altogether the annual U.S. investment in measurement is about $50 billion. Operation of the system is more than 90 percent self-financed through its own internal system of charges, fees, and so on. The remainder is contributed by the Federal, state, and local governments. Studies have been made of the growth pattern of manufacturing industries in relation to the amount they invest in measurement. It is strikingly evident that the industries growing most rapidly are those that invest, in proportion to output, the most in measurement. FUNCTION OF THE NATIONAL MEASUREMENT The essential function of the national measurement system is to provide a quantitative basis in measurement for (1) interchangeability and (2) decisions for action in all aspects of daily life-public affairs, commerce, industry, science, and engineering. Interchangeability is of fundamental importance in modern society. Once a measurement system with a set of agreed-upon units and standards has been established, it will serve as a firm basis for the interchange of goods and services in the mass markets of modern commerce, of machine parts and devices in industry, and of scientific and technical information. Such a system makes it possible for any plant to mass-produce materials, parts, and systems that are interchangeable with those made in plants in other parts of the country. Without this basis for interchangeability, the industrial economy we know today could not exist. Likewise, if results obtained in one laboratory are to be useful in another, they must be expressed in a measurement system common to both laboratories; otherwise, confusion would result when two laboratories attempted to exchange information. Twentieth-century man must make numerous decisions throughout the day, and many of these decisions are based on measurement. For example, an aircraft pilot must read a number of measurement output dials in order to make vital decisions during a flight. In previous times, with fewer planes traveling at slower speeds, less information was needed. But today, with commercial and private aircraft clogging major airports and new designs which permit air travel at supersonic speeds, an entire new range of highly accurate information must be immediately available to aid pilots in making split second decisions. Similiar needs exist in many areas of daily activity and especially in science and technology. Bureau scientists can measure time accurate to a few parts in 1012-many orders of magnitude greater than needed by the man on the street-but one hundred times less than the accuracy being sought by technicians involved in the space program. The needs of defense programs, high speed transportation systems, complex computer operations, and may more scientifically oriented activities made possible by the rapidly expanding technology demand readily available, highly accurate measurement. To the extent that the needed measurement and associated techniques are not available, technological advancement will be correspondingly hampered. To provide a basis for both interchangeability and decision-making throughout the Nation, all measurement must be compatible with each other. The airplane pilot's decisions based on measurement must be compatible with the measurement of others if he is to stay on course, avoid collisions, and arrive on time. Thus the system operates to provide "constrained freedom." That is, each manufacturer or businessman within the system has complete freedom to make his own decisions and to develop products as he wishes; but at the same time he is so constrained that his activities will be compatible with his environment and he will thus be able to operate successfully. THE INTELLECTUAL SYSTEM The intellectual, or conceptual measurement system, is the logical structure that binds together the measurables of science, industry, and commerce. The chain of logic starts with four independent, arbitrarily defined units for the basic quantities-length, mass, time, and temperature. These units (the meter, kilogram, second, and degree Kelvin) are defined by international agreement in such a way that changing the size of any one of them will have no effect on the size of any of the other three. From these four "basic units" are derived the units for all other physical quantities such as power, force, current, or resistance-in accordance with the definitions and equations of physics. The quantity of speed, for example, is obtained as a length divided by an interval of time. Once the units of length and time have been defined, a unit of speed can also be defined. The unit of speed is then a derived unit, dependent in size on the size of the units of length and time. In the same manner, the unit of acceleration is derived from the units of speed and time. Continuing in this way, one eventually arrives at a consistent system of units; that is, a system consistent with the equations of physics. This type of system has the important advantages of coherence and simplicity of computation. Using a consistent system of units, one can proceed by means of definitions and measurement rules to establish another category of measurables: the intrinsic properties of substances, such as density. This category includes a set of quantities very similar to the basic and derived physical quantities to which they are related by their definitions. Similarly, by means of definitions, relationships, and test schemes, one can go from the properties of substances to the performance characteristics of simple devices-for example the amplification factor of a vacuum tube or the sharpness of a razor blade. Then, proceeding in the same direction one can go to the performance criteria of systems-like the reliability of a computer-feeding in test schemes and formulations to form a progressive, coherent set of measurable quantities. In 1960 the International Conference on Weights and Measures adopted an International System of Units (abbreviated SI for Sys teme International). The SI is a consistent metric system of units based on six fundamental physical quantities in terms of which all others are to be defined so as to be consistent with the generally accepted equations of physics. These quantities and their units are mass (Kilogram), length (meter), time (second), temperature (degree Kelvin), current (ampere), and luminous intensity (candela). THE OPERATIONAL SYSTEM The operational system consists of people and organizations which insure proper linkage of the U.S. system to the international measurement system, analyse and work on the pool of unmet needs, and maintain and disseminate information on the reservoir of capability that users may draw upon. There are three major networks which comprise the operational aspects of the measurement system. First there is the instrument network which provides calibrated traceable instrumentation, consistent and compatible with the national standards, for making measurements. This network is tied to the intellectual system through the national standards of physical measurement. Then there is the data network which provides the user of the system with critically evaluated data on the intrinsic properties of materials— data that investigators have obtained in measurements based on the national standards. This network thus gives the user in many cases a "ready-made answer" to his measurement problem so that he does not need to make the measurement himself. The data network is related to the intellectual system through the national standards and the definitions of the properties of substances. Finally, there is the techniques network which tells the user of the system how to make meaningful measurements. This network disseminates knowledge to the user, through publications and other means, so that he will know, first, how to make a given measurement, and second, what it is meaningful for him to measure. The National Bureau of Standards plays a key role in the operation of each of these networks. The role is one of central Federal leadership, guiding the system as it operates through the voluntary cooperation of American science and industry. Because this leadership must come through general acceptance based on capability, NBS concentrates on generating meaningful outputs • developing and maintaining the national standards which serve as the basic core for the three networks providing calibration services and standard reference materials for the instrument network ⚫ generating and evaluating data for the data network developing methods of meaningful measurement for the techniques network. The Central Core The central or basic core of the national meaurement system consists of the four basic standards and some 50 derived standards. The basic four are national standards with coordinating links to international standards. They are developed by starting with a knowledge of materials as a basis for conceiving and defining a unit; then on to a material realization of this unit, and finally to the standard. With the exception of the kilogram, each of the four basic units is now defined in such as way as to be independently reproducible-the meter in terms of the wavelength of the red radiation from krypton-86, the degree Kelvin in terms of the triple point of water, and the second in terms of a transition of the cesium-133 atom. The derived standards are obtained by first defining the appropriate unit in terms of the basic units so that definitions will be consistent with the equations of physics; knowledge of materials can thus be used to realize this unit in as accurate a material form as possible. Instrumentation Network Leading outward from the central core of national standards, there is a chain of measurement that provides for measuring all the magnitudes man must deal with. In mass, for example, the range extends from the mass of the earth, or even beyond, down to the mass of the electron, neutron, or sub-particle. This is a vast spectrum of some 50 or 60 orders of magnitude that must be connected through a measurement chain to the defined unit, the kilogram, in order to provide the accuracy required by science and industry at any particular magnitude. Some of these magnitudes can be measured directly by taking multiples or submultiples of the standard, but as measurements are made farther and farther from the central part of the range, it is necessary to use indirect methods, with a corresponding reduction in accuracy. It is impossible for a single institution such as NBS to make calibrations over the complete range for mass or for any other quantity. The Bureau is thus forced to make basic decisions as to needed range and accuracy. It is Bureau policy to pick calibration points (or in some cases calibration regions) at intervals over the range so that the measurement activities of the country can be coupled to NBS at these points. The Bureau relies on other measurement laboratories in industry and Government to extend calibration to intermediate points between the NBS points, thus covering the range as needed. In this way the national standards in the central core are ultimately disseminated over the entire instrumentation network. To help in making the basic decisions that are required, NBS is now using accuracy charts to assess its measurement capabilities in various |