4. Choice of an existing method or the development of a new method

4. Choice of an existing method or the development of a new method

Development of a new method is based on an error budget and in the final method factors are specified which affect the measurement result, as follows:

4.1. Design

A measurement method can be described in terms of

  • measurement principle
  • procedures
  • equipment and
  • target values and tolerances (specifications) for operational performance and functionality

With access to modern computing, simulation can be used to advantage for example in this development work.

Metrological confirmation deals with methods of checking that critical functions and performances satisify specifications [ISO 10012].

Measurement equipment shall have those metrological characteristics demanded of the application at hand (for example concerning accuracy, stability, measurement range and resolution),

  • This means that one starts a measurement task by evaluating what is to measured,
  • Thereafter can suitable equipment be chosen.

A metrological characteristic is any distinguishing feature (of a measurement system) which can influence the results of measurement [ISO 10012:2002 §3.4]

Confirmation system

Here the aim is to limit the risk of unacceptable errors in measurement equipment. Suitable statistical methods are therefore recommended in order to analyse the results of earlier measurements/calibrations and with similar equipment.

  • A useful means of checking that a measurement instrument is reading correctly is by the measurer himself measures a check standard at regular intervals with the instrument [ISO 10012].

4.2. Calibration and corrections

which are used in calculating the measurement result.

Errors associated with calibration should be as small as possible.”For most measurement tasks calibrations errors should be less than a third and preferably only one tenth of the error permitted when using the confirmed equipment” [ISO 10012]

  • “Use of certified reference materials” ISO Guide 33
  • “Linear calibration using reference materials” ISO 11095

4.3. Check plan (self checking)

“Quality assurance for measuring equipment: Control of measuring processes” ISO 10012

4.4 Terminology

ISO 10012 Metrological confirmation for measuring equipment & processes

Processes of production &  measurement
Specification of measurement problem
Design of experiments
Specification of demands on a measurement system
Choice/development of a measurement method
Evaluation (validation) of a measurement method
Verification
Performing the measurements
Presentation of measurement results
Use of measurement results. Conformity assessment

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