Measurement Uncertainty from Sampling: Implication for Testing, Diagnostics and Inspection

Michael Ramsey

Abstract

Measurement uncertainty (MU) has become recognised as the primary metric of data quality for quantitative chemical measurements made in the laboratory (i.e. ex situ). Furthermore, the primary sampling of the material under consideration, is now generally considered to be the first step in the measurement process. It follows that the MU that arises from sampling (UfS) needs to be included in the overall estimate of MU. This principle also applies when measurements are made in situ, without removal of a physical sample, as is the case for most hand-held and locally positioned measurement devices. A worked example with Portable XRF is used to explain how MU and UfS can be estimated for in situ measurements. It is argued that this role of UfS within MU is equally applicable to quantitative measurements made for Testing, Diagnostics and Inspection in general, and will improve the reliability of compliance decision made on whatever material is under consideration.

Keywords

Measurement Uncertainty, Sampling, Testing, Guidance

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IMEKO TC

TC10 - Measurement for Diagnostics, Optimization and Control

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