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A technical standard is an established norm or requirement in regard to technical systems. It is usually a formal document that establishes uniform engineering or technical criteria, methods, processes and practices. In contrast, a custom, convention, company product, corporate standard, etc. that becomes generally accepted and dominant is often called a ''de facto'' standard. A technical standard can also be a controlled artifact or similar formal means used for calibration. Reference standards and certified reference materials have an assigned value by direct comparison with a reference base. A primary standard is a technical standard which is not subordinate to any other standard but serves to define the property in question. Primary standards are usually kept in the custody of a national standards body. A hierarchy of secondary, tertiary, and check standards are calibrated by comparison to the primary standard; only those on the lowest level are used for actual measurement work in a metrology system. A key requirement in this case is (metrological) traceability, an unbroken paper trail of calibrations back to the primary standard. A technical standard may be developed privately or unilaterally, for example by a corporation, regulatory body, military, etc. Standards can also be developed by groups such as trade unions, and trade associations. Standards organizations often have more diverse input and usually develop voluntary standards: these might become mandatory if adopted by a government, business contract, etc. The standardization process may be by edict or may involve the formal consensus〔Example of (TAPPI standards development regulations )〕 of technical experts. ==Types of standards== The primary types of technical standards are: * A ''standard specification'' is an explicit set of requirements for an item, material, component, system or service. It is often used to formalize the technical aspects of a procurement agreement or contract. For example, there may be a specification for a turbine blade for a jet engine that defines the exact material and performance requirements. * A ''standard test method'' describes a definitive procedure that produces a test result. It may involve making a careful personal observation or conducting a highly technical measurement. For example, a physical property of a material is often affected by the precise method of testing: any reference to the property should therefore reference the test method used. * A ''standard practice'' or procedure gives a set of instructions for performing operations or functions. For example, there are detailed standard operating procedures for operation of a nuclear power plant. * A ''standard guide'' is general information or options that do not require a specific course of action. * A ''standard definition'' is formally established terminology. * ''Standard units'', in physics and applied mathematics, are commonly accepted measurements of physical quantities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Technical standard」の詳細全文を読む スポンサード リンク
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