by Tray Eason
The 4:1 calibration ratio is still widely referenced in industrial quality systems and procurement language. Many organizations treat it as a requirement for good calibration, and some treat it as an acceptance criterion. That use does not match the historical intent of ratio-based practices or the requirements of modern accredited calibration.
Modern calibration standards are built on quantified measurement uncertainty and documented decision rules. Fixed ratios such as 4:1 do not control decision risk for individual measurements. This article explains where 4:1 originated, how TAR and TUR differ, why ratios persist, and what ISO/IEC 17025 and ILAC guidance actually require for conformity assessment.
Be the first to comment