TUR / TAR check

Check a test uncertainty ratio against 4:1 or your own target, for symmetric, asymmetric and one-sided tolerances, and find the U95 you would need to reach it. TAR is shown separately as the older ratio that ignores the full calibration process uncertainty.

TUR · test uncertainty ratio

v0.1.0 · Z540.3 §3.11

ToleranceNominal± tolerance TU95 of the calibration processTarget ratio (x : 1)Reference accuracy ± (for TAR, optional)

TUR4.00 : 1meets 4 : 1 · symmetric tolerance · U95 needed for 4 : 1 is 0.0025 or less

TUR = (upper − lower) ÷ (2 × U95) · one-sided: |limit − nominal| ÷ U95 · all values in one unit · U95 is the whole process at about 95 %

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How this is calculated

Equation: TUR = (upper − lower) / (2 × U95); one-sided: TUR = |limit − nominal| / U95; required U95 = (upper − lower) / (2 × target); TAR = tolerance half-width / reference accuracy
Source: TUR as defined in ANSI/NCSL Z540.3-2006 §3.11 (withdrawn by NCSLI in October 2020; still used in contracts and in ANAB’s Z540.3 supplemental accreditation). One-sided handling is Metrology Bench’s stated convention: the distance from nominal to the single limit is used as the half-span, which reduces to §3.11 for a symmetric tolerance. TAR is the older accuracy-spec ratio (MIL-STD-45662A era) and ignores the full calibration process uncertainty.
Valid range: U95 > 0; upper > lower; nominal inside the tolerance; target > 0
Rounding: Ratios shown to 2 decimal places, rounded half up; the target comparison uses full precision.
Version: v0.1.0 · changelog

Calculated value, not a certified result. Accredited laboratories must validate any software they use (ISO/IEC 17025 clause 7.11).

Test vectors for this tool

The reference cases this calculator is tested against on every change. Use them to check your own software. All test vectors · Download JSON

ID	Inputs	Expected	Tolerance	Source
TUR-01	lower = -0.001, upper = 0.001, U95 = 0.0006, output = tur	1.6666666666666667 ratio	± 1e-12	ANSI/NCSL Z540.3-2006 §3.11 TUR definition, TUR = (upper − lower)/(2 × U95). Withdrawn by NCSLI in October 2020; still used in contracts and ANAB’s Z540.3 supplement. Clause number and definition confirmed from NASA sources that quote it (Mimbs, NASA NTRS 20130011498; NASA-HDBK-8739.19-4 §3.5.1); withdrawal date from NCSLI’s Z540.3 page.
TUR-02	lower = -10, upper = 10, U95 = 2.5, output = tur	4 ratio	± 1e-12	ANSI/NCSL Z540.3-2006 §3.11 TUR definition, TUR = (upper − lower)/(2 × U95). Withdrawn by NCSLI in October 2020; still used in contracts and ANAB’s Z540.3 supplement. Clause number and definition confirmed from NASA sources that quote it (Mimbs, NASA NTRS 20130011498; NASA-HDBK-8739.19-4 §3.5.1); withdrawal date from NCSLI’s Z540.3 page.
TUR-03	lower = 9.95, upper = 10.1, nominal = 10, U95 = 0.02, output = tur	3.75 ratio	± 1e-12	ANSI/NCSL Z540.3-2006 §3.11 TUR definition, TUR = (upper − lower)/(2 × U95). Withdrawn by NCSLI in October 2020; still used in contracts and ANAB’s Z540.3 supplement. Clause number and definition confirmed from NASA sources that quote it (Mimbs, NASA NTRS 20130011498; NASA-HDBK-8739.19-4 §3.5.1); withdrawal date from NCSLI’s Z540.3 page.
TUR-04	nominal = 100, upper = 105, U95 = 1.25, output = tur	4 ratio	± 1e-12	Metrology Bench one-sided convention, derived from Z540.3 §3.11: TUR = \|limit − nominal\| / U95 (the tolerance mirrored about the nominal); not text from Z540.3
TUR-05	nominal = 50, lower = 49, U95 = 0.5, output = tur	2 ratio	± 1e-12	Metrology Bench one-sided convention, derived from Z540.3 §3.11: TUR = \|limit − nominal\| / U95 (the tolerance mirrored about the nominal); not text from Z540.3
TUR-06	lower = -10, upper = 10, target = 4, output = requiredU95	2.5 same as U95	± 1e-12	ANSI/NCSL Z540.3-2006 §3.11 TUR definition, TUR = (upper − lower)/(2 × U95). Withdrawn by NCSLI in October 2020; still used in contracts and ANAB’s Z540.3 supplement. Clause number and definition confirmed from NASA sources that quote it (Mimbs, NASA NTRS 20130011498; NASA-HDBK-8739.19-4 §3.5.1); withdrawal date from NCSLI’s Z540.3 page.
TUR-07	nominal = 100, upper = 105, target = 4, output = requiredU95	1.25 same as U95	± 1e-12	Metrology Bench one-sided convention, derived from Z540.3 §3.11: TUR = \|limit − nominal\| / U95 (the tolerance mirrored about the nominal); not text from Z540.3
TUR-08	lower = -10, upper = 10, referenceAccuracy = 1, output = tar	10 ratio	± 1e-12	TAR, the older accuracy-spec ratio (MIL-STD-45662A era): UUT accuracy ÷ reference accuracy
TUR-09	upper = 105, U95 = 1.25, output = tur	RangeError ratio	exact	Metrology Bench rule: never guess a missing piece
TUR-10	lower = 10, upper = -10, U95 = 1, output = tur	RangeError ratio	exact	Input check
TUR-11	lower = -10, upper = 10, U95 = 0, output = tur	RangeError ratio	exact	Input check

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