Metrology

Related guides

• Calibration certificates

  How calibration results, corrections, uncertainty, traceability and conformity statements describe different aspects of measurement evidence.

• Calibration intervals

  Setting and reviewing recalibration schedules using measurement needs, drift, usage, checks, and consequences rather than a universal annual rule.

• Cp process capability

  Tolerance-to-spread ratio, estimation assumptions, within versus overall variation and limits on interpreting capability.

• Cpk process capability

  Centering-sensitive capability, within versus overall variation, one-sided limits, confidence bounds and interpretation.

• Gauge repeatability and reproducibility

  Designing and interpreting Gage R&R studies without confusing precision, bias, variance percentages and tolerance consumption.

• Guard bands in conformity assessment

  Separating specification and acceptance limits, selecting uncertainty-aware decision rules, and interpreting false-accept and false-reject risks.

• Instrument resolution

  Display increments, effective discrimination, quantization uncertainty and practical limits on selecting measurement equipment.

• Measurement bias

  Estimating systematic measurement offsets against references, with controls for correction, range, uncertainty and decision use.

• Measurement decision rules

  Choosing, agreeing, applying, and reporting uncertainty-aware conformity decisions without confusing a measured result with acceptance.

• Measurement repeatability

  Precision under defined short-term conditions, repeatability study design, standard-deviation estimation and uncertainty limits.

• Measurement reproducibility

  Evaluating precision under changed measurement conditions, with clear study boundaries, variance models and uncertainty limits.

• Measurement traceability

  Connecting measurement results to stated references through calibration chains, uncertainties, competent services, and controls during use.

• Measurement uncertainty

  Measurement models, Type A/B evaluation, combined and expanded uncertainty, worked budgets and conformity decisions.

• Pp process performance

  Interpreting Pp as specification width relative to overall process spread, with centering, sampling and distribution limits.

• Ppk process performance

  Calculating and interpreting overall process performance with representative data, explicit variation estimators, distribution checks, and uncertainty about the index.

• Reference standards

  Metrological reference and working standards, certified reference materials, traceability, certificate interpretation and continued validity.

• Sampling length in surface measurement

  Separating legacy sampling lengths, ISO 21920 evaluation and section lengths, filter scales and digital point spacing.

• Surface roughness cutoff length

  Interpreting profile-filter settings, legacy sampling lengths, ISO 21920 nesting indices, and evaluation lengths without assuming a universal cutoff.