Official Publications
These are the authoritative documents that define and support ITS-90 implementation worldwide.
📋 ITS-90 Official Text
Bureau International des Poids et Mesures (BIPM)
The complete official text of the International Temperature Scale of 1990, including all definitions, equations, and fixed point data.
📖 Supplementary Information for ITS-90
Consultative Committee for Thermometry (CCT)
Additional technical information, corrections, and clarifications to support ITS-90 implementation.
🔬 Mise en Pratique
BIPM - Kelvin Definition
Practical realization guidelines for the kelvin following the 2019 SI redefinition.
Important: 2019 SI Redefinition of the Kelvin
In May 2019, the International System of Units (SI) was fundamentally revised. The kelvin is now defined by fixing the numerical value of the Boltzmann constant to exactly 1.380 649 × 10⁻²³ J·K⁻¹, rather than being based on the triple point of water. While ITS-90 implementation remains largely unchanged, this redefinition provides a more fundamental basis for temperature measurement.
The BIPM mise en pratique for the kelvin provides detailed guidance on practical realization of the new definition and its relationship to ITS-90.
National Metrology Institutes
National metrology institutes maintain primary temperature standards and provide calibration services, training, and technical support.
🇺🇸 NIST (United States)
National Institute of Standards and Technology
Temperature and humidity calibration services, SRMs, and extensive technical publications.
🇬🇧 NPL (United Kingdom)
National Physical Laboratory
Temperature metrology research, calibration services, and measurement guides.
🇩🇪 PTB (Germany)
Physikalisch-Technische Bundesanstalt
Primary temperature standards, research, and international comparisons.
🇫🇷 LNE (France)
Laboratoire National de Métrologie et d'Essais
Temperature metrology services and research programmes.
🇯🇵 NMIJ (Japan)
National Metrology Institute of Japan
Temperature standards and advanced thermometry research.
🌐 Other NMIs
International Network
Temperature metrology institutes worldwide providing regional support.
Technical Standards & Guidelines
ASTM Standards
- ASTM E1137 - Standard Specification for Industrial Platinum Resistance Thermometers
- ASTM E563 - Standard Practice for Preparation and Use of an Ice-Point Bath
- ASTM E644 - Standard Test Methods for Testing Industrial Resistance Thermometers
IEC Standards
- IEC 60751 - Industrial platinum resistance thermometers and platinum temperature sensors
- IEC 60584 - Thermocouples (multiple parts covering types, tolerances, and reference functions)
ISO Standards
- ISO 80000-5 - Quantities and units - Part 5: Thermodynamics
- ISO/IEC Guide 98-3 - Uncertainty of measurement (GUM)
Stay Updated
This page is updated regularly to reflect the latest developments in temperature metrology. For the most current information and recent amendments, we encourage users to consult the official BIPM and CCT websites directly.
Temperature metrology is an active field with ongoing research and development. Stay informed about the latest developments through professional organizations, technical publications, and regular training updates.
For questions about specific technical aspects of ITS-90 implementation, consult with your national metrology institute or experienced temperature metrology professionals.