Three fundamental issues must be addressed when evaluating a measurement system:
1) The measurement system must demonstrate adequate sensitivity.
First, does the instrument (and standard) have adequate discrimination? Discrimination (or class) is fixed by design and serves as the basic starting point for selecting a measurement system. Typically, the Rule of Tens has been applied, which states that instrument discrimination should divide the tolerance (or process variation) into ten parts or more.
Second, does the measurement system demonstrate effective resolution? Related to discrimination, determine if the measurement system has the sensitivity to detect changes in product or process variation for the application and conditions.
2) The measurement system must be stable.
Under repeatability conditions, the measurement system variation is due to common causes only and not special (chaotic) causes.
The measurement analyst must always consider practical and statistical significance.
3) The statistical properties (errors) are consistent over the expected range and adequate for the purpose of measurement (product control or process control).
The long-standing tradition of reporting measurement error only as a percent of tolerance is inadequate for the challenges of the marketplace that emphasize strategic and continuous process improvement. As processes change and improve, a measurement system must be re-evaluated for its intended purpose. It is essential for the organization (management, measurement planner, production operator, and quality analyst) to understand the purpose of measurement and apply the appropriate evaluation.
source of Measurement Issues: Analysis of measurement systems
