Overview
ISO/TR 16015:2003 - "Geometrical product specifications (GPS) - Systematic errors and contributions to measurement uncertainty of length measurement due to thermal influences" provides procedures to identify, correct and quantify the effects of thermal influences on length measurement results. The Technical Report is intended for cases where thermal effects are a significant contributor to measurement uncertainty or systematic error in GPS activities. It defines practical evaluation steps for measurements made at or away from the standard reference temperature and for time-varying temperature conditions.
Key topics and requirements
- Scope and cases considered
- Measurements at the standard reference temperature.
- Measurements at non-reference temperatures with user-applied corrections.
- Measurements at non-reference temperatures without corrections.
- Thermal expansion concepts
- Definitions of coefficient of thermal expansion (nominal, measured) and related uncertainties.
- Thermal expansion, differential thermal expansion, and corrected length concepts.
- Uncertainty evaluation
- Procedures to evaluate uncertainties of workpiece and working-standard temperatures, coefficients of thermal expansion and resulting length uncertainty.
- Formula relationships provided in the report (for example, uncertainty in thermal expansion due to α: uE(L) = L · θ · u(α)) and combined treatment of contributors following the Guide to the Expression of Uncertainty in Measurement (GUM).
- Temporal and environmental effects
- Treatment of time-dependent temperature variation, thermal response times and dimensional response.
- Advisory guidance on temperature environment and drift testing (Annex A) plus worked example (Annex B).
- Limitations
- Temperature gradients are noted but are not covered in full detail - users must take extra care where gradients exist.
Applications
ISO/TR 16015 is practical for:
- Calibration laboratories and metrologists performing length calibrations and uncertainty budgets.
- Quality and inspection engineers responsible for dimensional verification under GPS.
- Manufacturers and suppliers of precision components where thermal effects influence conformance decisions.
- Developers of measurement procedures and comparators needing thermal correction methods.
Practical uses include deciding whether to correct measurements for thermal differences, calculating thermal contributions to combined standard uncertainty, and supporting conformance decisions where thermal uncertainty is significant.
Who should use it
- Metrology labs, calibration service providers, and inspectors working with precision length measurements.
- Engineers implementing GPS-compliant verification processes and uncertainty assessments.
- Standards specialists integrating thermal considerations into product specification and test plans.
Related standards
- ISO 1 - Standard reference temperature for geometrical product specification and verification
- GUM - Guide to the Expression of Uncertainty in Measurement
- ISO/TS 14253-2 and ISO 14253-1 - decision rules and broader GPS analysis methods
Using ISO/TR 16015 helps ensure robust, traceable treatment of thermal effects in length measurement and clearer, defensible uncertainty statements for GPS tasks.