Overview
EN ISO 1:2022 - Geometrical product specifications (GPS) - Standard reference temperature for the specification of geometrical and dimensional properties (ISO 1:2022) - defines the concepts of reference temperature and the standard reference temperature used when specifying geometrical and dimensional properties of objects. The standard fixes the internationally agreed value of the standard reference temperature at t = 20 °C (according to ITS‑90). It is published as a CEN-adopted European standard (EN ISO 1:2022) and supersedes EN ISO 1:2016.
Key topics and requirements
- Standard reference temperature value: The standard reference temperature is 20 °C (ITS‑90) and is the default reference for specifying dimensions, geometry and related measurands unless another temperature is explicitly stated.
- Definitions: Clarifies the terms reference temperature (the uniform temperature specified for a geometrical property) and standard reference temperature (the internationally agreed value).
- Scope of application: Applies to geometrical and dimensional properties including size, location, orientation (angles), form and surface texture, and to the definition of the measurand used in verification or calibration.
- Non‑standard temperatures: Allows specification of a different reference temperature when required, provided it is explicitly stated; warns that using non‑standard temperatures can increase measurement uncertainty.
- Measurement and verification implications: Notes that measurements rarely occur at the exact reference temperature, so temperature correction or accounting for the temperature difference in the measurement uncertainty budget is necessary.
- Reference to ITS‑90: States temperature values in EN ISO 1:2022 are to be interpreted according to the International Temperature Scale of 1990 (ITS‑90) (see Annex B).
Applications and who uses it
- Design engineers and product developers: Specify unambiguous dimensional requirements on drawings and CAD models referenced to a common temperature.
- Metrology and calibration laboratories: Define measurands and calibrate gauge blocks, CMMs and other instruments against the standard reference temperature.
- Quality and inspection teams in manufacturing: Apply consistent inspection criteria and uncertainty evaluation when verifying parts against drawings or specifications.
- Standards writers and procurement specialists: Reference a harmonized temperature baseline in technical product documentation and contracts.
Related standards
- ISO/IEC Guide 99 (VIM) - terminology and metrology concepts referenced in EN ISO 1:2022
- ISO/IEC Guide 98‑3 (GUM) - measurement uncertainty principles (referred to in guidance)
- ISO/TR 16015 - additional guidance on temperature effects for dimensional measurements
- ISO 14638 - GPS fundamentals (EN ISO 1:2022 is a fundamental GPS standard)
EN ISO 1:2022 ensures consistent, internationally accepted temperature referencing for dimensional specifications, improving clarity in design, calibration and verification across industries.