ISO 80000-11:2019/AMD1:2025

Overview

ISO 80000-11:2019/AMD1:2025 is the first amendment to the international standard ISO 80000-11, titled Quantities and units - Part 11: Characteristic numbers. Published by ISO in collaboration with the IEC and CEN, this 2025 update refines and supplements the definitions, symbols, and units related to characteristic numbers within the International System of Units (SI). It ensures harmonized terminology and unit representations for consistent scientific and engineering applications worldwide.

Characteristic numbers, such as dimensionless quantities and dimensionless constants, are fundamental for expressing relationships in physics, engineering, and other applied sciences. This amendment strengthens the reference framework by incorporating essential updates to normative references and clarifying terms and definitions.

Key Topics

• Normative References Update:
  The amendment adds the 9th edition (2019) of The International System of Units (SI) by BIPM as a normative reference, providing required backing for units and definitions presented.

• Terms and Definitions Refinement:
  The standard modifies the description of characteristic numbers, emphasizing that names, symbols, definitions, and units for these quantities are provided in detailed tables (Tables 1 to 6) and consistent with the SI.

• Harmonization with SI:
  The document aligns characteristic numbers explicitly with the International System of Units to maintain coherence across related standards in measurements, calculations, and technical communication.

• Collaboration Across Bodies:
  This amendment reflects efforts from ISO Technical Committee 12 (Quantities and units), IEC Technical Committee 25, and CEN, ensuring a broad consensus and relevance for international electrotechnical and general measurement standards.

Applications

• Scientific Research:
  Provides universally accepted characteristic numbers and unit representations critical for experimental data reporting in physics, chemistry, and engineering disciplines.

• Technical Engineering:
  Facilitates precise design, analysis, and documentation in mechanical, electrical, and civil engineering projects requiring dimensionless parameters like Reynolds number, Mach number, or Prandtl number.

• Standards Development:
  Supports developers of international and national measurement regulations by establishing standardized characteristic number definitions aligned with SI units.

• Education and Training:
  Serves as an authoritative resource in academic curricula and professional training on metrology and measurement sciences, fostering consistent understanding and usage of quantities and units.

• Software and Instrumentation:
  Assists manufacturers and software developers in accurate representation and interpretation of characteristic numbers within instrumentation, simulation, and data processing tools.

Related Standards

• ISO 80000 Series:
  This amendment belongs to the ISO 80000 series - an all-encompassing collection addressing quantities and units across different physical domains, including space and time (Part 1), mechanics (Part 4), and thermodynamics (Part 6).

• BIPM SI Brochure (9th edition, 2019):
  The core reference defining base and derived units, prefixes, and fundamental constants essential for implementing ISO 80000-11 amendment.

• IEC/ISO 80000 Joint Publications:
  Coordination with IEC TC 25 ensures consistent electrotechnical standardization related to quantities and characteristic numbers.

• ISO/IEC Directives, Part 1 and 2:
  Governs the standard development process and editorial rules applicable to ISO 80000-11 and its amendments.

Summary

ISO 80000-11:2019/AMD1:2025 Amendment 1 enhances the clarity, accuracy, and alignment of characteristic numbers and their associated units within international metrology standards. By updating normative references, refining definitions, and reinforcing conformity with the International System of Units, this standard plays a vital role in ensuring interoperability, precision, and clarity in scientific, engineering, and industrial communication involving dimensionless quantities.