Ministry of Education and Science of Ukraine National Aviation University Lecture Notes compiler О.Bashta 1 Lecture 1 Subject and tasks of metrology 1. Subject of Metrology 2. Physical quantities and their units 3. The international system of units 4. A metrology system creation 1. Subject of Metrology Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement. Metrology is defined by the International Bureau of Weights and Measures (BIPM) as "the science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology."[1] The ontology and international vocabulary of metrology (VIM) is maintained by the International Organisation for Standardisation. The International Bureau of Weights and Measures (French: Bureau international des poids et mesures), is an international standards organisation, one of three such organisations established to maintain the International System of Units (SI) under the terms of the Metre Convention (Convention du Mètre). The organisation is usually referred to by its French initialism, BIPM. The other organisations that maintain the SI system, also known by their French initialisms are the General Conference on Weights and Measures (French: Conférence générale des poids et mesures) (CGPM) and the International Committee for Weights and Measures (French: Comité international des poids et mesures) (CIPM). Measurement - finding values of physical quantities experimentally. Quantity - property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference The unity of measurements - this state when measuring physical quantities are expressed in terms of legitimate and known values of their errors with a given probability. The basic issues of metrology are: 1. The general theory of measurement; 2. Units of physical quantities and their systems; 3. Methods and means of measurement; 4. Methods for determining the accuracy of measurements; 5. Principles of unity and uniformity of measurements of the measurement instruments; 6. Methods of transmission units, from the standards or model of measuring working means of measurement. Metrology is a very broad field and may be divided into three subfields: Subfield Definition Scientific or concerns the establishment of quantity systems, unit systems, units of fundamental measurement, the development of new measurement methods, realisation of metrology measurement standards and the transfer of traceability from these standards to 2 users in society. Applied or concerns the application of measurement science to manufacturing and other industrial processes and their use in society, ensuring the suitability of measurement metrology instruments, their calibration and quality control of measurements. concerns regulatory requirements of measurements and measuring instruments Legal metrology for the protection of health, public safety, the environment, enabling taxation, protection of consumers and fair trade. Metrology operates a number of terms set DSTU 2681-94 "Metrology. Terms and definitions ". This standard sets the requirements for usage of terms in all kinds of documentation, scientific, educational literature, which belongs to metrology and metrological support, and work on standardization, or when using the results of these works, including software for computers' computer systems. Here are the characteristics of the most used of standardized terms: фізична величина - властивість, спільна в якісному відношенні для багатьох матеріальних об'єктів та індивідуальна в кількісному відношенні для кожного з них; quantity property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference. The concept ‘quantity’ may be generically divided into, e.g. ‘physical quantity’, ‘chemical quantity’, and ‘biological quantity’, or base quantity and derived quantity. розмір (фізичної) величини - кількісний вміст фізичної величини в даному об'єкті; kind of quantity aspect common to mutually comparable quantities. NOTE 1 The division of the concept of „quantity‟ according to „kind of quantity‟ is to some extent arbitrary. EXAMPLE 1 The quantities diameter, circumference, and wavelength are generally considered to be quantities of the same kind, namely of the kind of quantity called length. EXAMPLE 2 The quantities heat, kinetic energy, and potential energy are generally considered to be quantities of the same kind, namely of the kind of quantity called energy. значення (фізичної) величини - відображення фізичної величини у вигляді числового значення величини із позначенням її одиниці; істинне значення (фізичної величини) - значення фізичної величини, яке ідеально відображало б певну властивість об'єкта; умовно істинне значення (фізичної величини) - значення фізичної величини, знайдене експериментальним шляхом і настільки наближене до істинного значення, що його можна використати замість істинного для даної мети (дійсне значення); система (фізичних) величин - сукупність взаємопов'язаних фізичних величин, в якій декілька величин приймають за незалежні, а інші визначають як залежні від них; 3 system of quantities set of quantities together with a set of noncontradictory equations relating those quantities NOTE Ordinal quantities, such as Rockwell C hardness, are usually not considered to be part of a system of quantities because they are related to other quantities through empirical relations only. основна (фізична) величина - фізична величина, що входить до системи фізичних величин і прийнята за незалежну від інших величин цієї системи; base quantity quantity in a conventionally chosen subset of a given system of quantities, where no subset quantity can be expressed in terms of the others. NOTE 2 Base quantities are referred to as being mutually independent since a base quantity cannot be expressed as a product of powers of the other base quantities. похідна (фізична) величина - фізична величина, що входить до системи величин та визначається через основні величини цієї системи; derived quantity quantity, in a system of quantities, defined in terms of the base quantities of that system EXAMPLE In a system of quantities having the base quantities length and mass, mass density is a derived quantity defined as the quotient of mass and volume (length to the third power). розмірність фізичної величини - вираз, що відображає її зв'язок із основними величинами системи; одиниця (фізичної) величини - фізична величина певного розміру, прийнята за угодою для кількісного відображення однорідних з нею величин; числове значення (фізичної) величини - число, що дорівнює відношенню розміру фізичної величини, що вимірюється, до розміру одиниці цієї фізичної величини чи кратної одиниці; 2. Physical quantities and their units There are an unlimited number of derived units formed from multiplication and division of the seven base units;[12] for example, the SI derived unit of speed is metre per second, m/s. Some derived units have special names; for example, the unit of resistance, the ohm, symbol Ω, is uniquely defined by the relation Ω = m2·kg·s−3·A−2, which follows from the definition of the quantity electrical resistance. The radian and steradian, once given special status, are now considered derived units.[12] Technical measurement is an integral part of applied metrology. The process of measurement is characterized on the one hand, perception and reflection of a physical quantity, and on the other - normalization, i.e. the assignment of a numerical value (size), which is expressed in the adopted units. The values of quantities should not be equated with the size. The size of the physical quantity of the object really exists and whether we know or not express it in any terms. The value of the same physical quantity appears only after the size value of this object is expressed by a particular unit. The values of physical quantities get due to reach the measurement or calculation. 4 Writing unit symbols and the values of quantities The value of a quantity is written as a number followed by a space (representing a multiplication sign) and a unit symbol; e.g., "2.21 kg", "7.3×102 m2", "22 K". This rule explicitly includes the percent sign (%). Exceptions are the symbols for plane angular degrees, minutes and seconds (°, ′ and ″), which are placed immediately after the number with no intervening space.[13][14] Symbols for derived units formed by multiplication are joined with a centre dot (·) or a non-break space, for example, "N·m" or "N m". Symbols for derived units formed by division are joined with a solidus (⁄), or given as a negative exponent. For example, the "metre per second" can be written "m⁄s", "m s−1", "m·s−1" or . Only one solidus should be used; e.g., "kg⁄(m·s2)" or "kg·m−1·s−2" are acceptable but "kg⁄m⁄s2" is ambiguous and unacceptable. Many computer users will type the / character provided on computer keyboards, which in turn produces the Unicode character U+002F, which is named solidus but is distinct from the Unicode solidus character, U+2044. Symbols are mathematical entities, not abbreviations, and do not have an appended period/full stop (.). Symbols are written in upright (Roman) type (m for metres, s for seconds), so as to differentiate from the italic type used for variables (m for mass, s for displacement). By consensus of international standards bodies, this rule is applied independent of the font used for surrounding text.[15]