Compute NDC = 1.41 × PV/GRR from part-to-part variation and measurement system error; NDC ≥ 5 is considered effective.
输入零件间变差 PV 与测量系统误差 GRR，求 NDC。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Number of distinct categories | ndc = 1.41 · PV / GRR, truncated to an integer | AIAG, Measurement Systems Analysis (MSA) Reference Manual, 4th ed. (2010) |
| Criterion | ndc ≥ 5 indicates the system can distinguish differences between parts | AIAG, Measurement Systems Analysis (MSA) Reference Manual, 4th ed. (2010) |
| Relation to %GRR | ndc complements %GRR in assessing measurement system discrimination | AIAG, Measurement Systems Analysis (MSA) Reference Manual, 4th ed. (2010) |
| Part variation | PV is the true variation between parts and forms the numerator of ndc | AIAG, Measurement Systems Analysis (MSA) Reference Manual, 4th ed. (2010) |