Assessment of measurement uncertainty for calibration and testing of testing and calibration laboratories in ISO / IEC 17025.

Guidance of assessing of measurement uncertainty - Testing  and calibration laboratories in ISO / IEC 17025

Assessment of measurement uncertainty for calibration / testing is an important technical requirement in ISO / IEC 17025 and is also an important indicator to assess laboratory capacity.

The measurement uncertainty is the parameters associated with the measurement result characterizing the dispersion of the value can be attributed to a measure in a reasonable manner. For testing or calibration laboratories perform internal calibration that is required to have procedures for evaluating the measurement uncertainty to all calibrations. Particularly with experimental activity, laboratory also must apply procedures for evaluating measurement uncertainty.

However in certain cases, the nature of the test method has limited the strict calculation in terms of measuring and statistic the measurement uncertainty. In this case, the laboratory should try to identify all components of the measurement uncertainty, conducting a reasonable evaluation to ensure results are not wrong impression about the measurement uncertainty.

The necessary strict level for assessing the measurement uncertainty depends on factors such as:

- The requirement of testing methods

- The requirement of customers

The limitations as a basis for decisions about conformity with technical regulations.

In case, a test method has been widely recognized which regulating the value limit of main sources causing the measurement uncertainty and define how to present the results calculated, the laboratory considered as to meet by following the test method.

It should be noted, the factors contribute to the measurement uncertainty include:

- Human factor

- Facility and environmental condition

- Testing and calibration Methods

- Device

- Linkages of measurement standards

- Reference standards or standard sample

The level of above factors, without limitation, will contribute to the general uncertainty of the measurements that the laboratory should consider before establishing methods and procedures for testing and calibration.

Article was written by the Technical Commitee - VINTECOM International from the general requirements for the competence of testing and calibration laboratories

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