How to Calculate a Complete Calibration Uncertainty Budget (GUM Method: Type A & Type B)

ISO/IEC 17025 Clause 7.6 mandates that all calibration results be reported with an associated expanded measurement uncertainty.

1. Type A vs Type B Sources

Type A represents repeatability standard deviation. Type B includes reference standard certificate uncertainty, digital display resolution, and thermal stability gradients.

2. Combined and Expanded Uncertainty

Combine variances via root-sum-squares. Multiply by coverage factor k=2 for a 95.45% confidence interval.