Overview
ISO/IEC Guide 98-3:2008/Amd 1:2026 is an internationally recognized amendment to the core guidance on the expression of uncertainty in measurement (GUM:1995). Published by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), this amendment specifically addresses the handling of nonlinearity in measurement models when evaluating measurement uncertainty. This guide ensures that measurement results are comparable and meaningful across scientific, industrial, and regulatory fields worldwide.
Key Topics
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Nonlinearity in Measurement Models
The amendment focuses on the identification and treatment of significant nonlinearities that affect measurement uncertainty analysis. For many real-world measurement systems, relationships between variables are not strictly linear, making this guidance critical for accurate uncertainty estimation.
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Use of Monte Carlo Methods
When nonlinearity is significant, the amendment recommends using Monte Carlo methods, as detailed in JCGM 101:2008, to better estimate uncertainty distributions. This approach provides a robust alternative to linearization techniques in complex measurement models.
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Higher-Order Taylor Series Expansions
The amendment outlines the need to consider higher-order terms in the Taylor series expansion of the measurement function. Inclusion of these terms becomes essential when linear approximations are insufficient for describing the system's behavior.
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Augmented Uncertainty Calculations
For significant nonlinear effects, both the estimate of the quantity of interest and the combined standard uncertainty must be recalculated to incorporate second-order and possibly higher-order influences.
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Bibliographic References
The document updates the related bibliography to include references to supplementary guidance, such as JCGM 101:2008 on the propagation of distributions using Monte Carlo methods.
Applications
This amendment is valuable across multiple domains where measurement uncertainty has a substantial impact:
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Calibration and Testing Laboratories
Ensures laboratories can deliver accurate and credible measurement results, specifically when nonlinearity is present in calibration processes.
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Quality Assurance and Metrology
Supports organizations in demonstrating competence and compliance with international measurement standards, essential for ISO/IEC 17025 accreditation.
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Scientific Research
Assists researchers in assessing and reporting measurement uncertainty, leading to more reproducible and trusted outcomes.
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Industrial Measurement Systems
Provides manufacturers, especially those dealing with advanced sensors and automation, with tools for rigorous uncertainty evaluation in nonlinear measurement models.
Related Standards
For more comprehensive guidance on measurement uncertainty and related methodologies, consult the following standards:
By incorporating the recommendations in this amendment, users ensure that their uncertainty analyses are robust, transparent, and aligned with the latest international metrological best practices.
Open preview (PDF)Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) — Amendment 1: Nonlinearity in measurement models
