2.
Measurement Process Characterization
2.1.
Characterization
2.1.1.
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What are the issues for characterization?
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'Goodness' of measurements
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A measurement process can be thought of as a well-run
production process in which measurements are the output.
The 'goodness' of measurements is the issue, and goodness
is characterized in terms of the errors that affect the measurements.
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Bias, variability and uncertainty
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Requires ongoing statistical control program
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The continuation of goodness is guaranteed by a statistical control program that controls both
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Scope is limited to ongoing processes
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The techniques in this chapter are intended primarily for
ongoing processes. One-time tests and special tests or
destructive tests are difficult to characterize. Examples of
ongoing processes are:
- Calibration where similar test items are measured on a regular basis
- Certification where materials are characterized on a regular basis
- Production where the metrology (tool) errors may be significant
- Special studies where data can be collected over the life of
the study
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Application to production processes
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The material in this chapter is pertinent to the study of
production processes for which the size of the metrology (tool)
error may be an important consideration. More specific guidance
on assessing metrology errors can be found in the section on
gauge studies.
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