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Showing 1591–1620 of 1709 reference entries

PhysicsSpecular and diffuse reflection

Reflection angles are measured from the local normal.

ModelPhysicsTotal internal reflection and evanescent fields

Total reflected flux does not mean zero field beyond the interface.

ModelPhysicsSpherical-mirror images and signs

A virtual image is formed by ray extensions, not actual ray convergence.

ModelPhysicsPhotoelectric threshold and stopping potential

Photon frequency sets maximum photoelectron energy in the single-photon model.

ModelPhysicsDe Broglie wavelength and particle momentum

A momentum state has a spatial wave phase.

ModelMeasurementQuantity kind and physical dimension

Equal dimensions do not make quantities interchangeable.

DefinitionMeasurementQuantity value, numerical value and unit

A numerical value depends on the chosen unit.

DefinitionMeasurementCoherent derived units

Coherence means no extra numerical factor in the base-unit product.

DefinitionMeasurementOrdinal quantities and nominal properties

Ordering and category labels do not justify ordinary arithmetic.

DefinitionMeasurementMeasurement principle, method and procedure

A physical phenomenon, an approach and a detailed procedure have different roles.

DefinitionMeasurementMeasuring instrument and measuring system

A complete measurement system can include more than one device.

DefinitionMeasurementSensor, transducer and detector

Component names describe different measurement roles.

DefinitionMeasurementInstrument indication and measurement result

A displayed reading is only one part of a measurement result.

DefinitionMeasurementAdjustment, calibration and zero adjustment

Changing an instrument response differs from determining its calibration.

DefinitionMeasurementReference and conventional quantity values

An accepted comparison value need not be an exact true value.

DefinitionMeasurementIndication interval, measuring interval and span

Possible readings differ from a validated interval of measurement.

DefinitionMeasurementRated operating conditions

Instrument properties are specified within a domain of use.

DefinitionMeasurement · ChemistrySelectivity of a measuring system

Responding to a target differs from excluding interference.

DefinitionMeasurementDiscrimination threshold and dead band

An undetected input change differs from an interval with no output change.

DefinitionMeasurementStability of a measuring instrument

Time stability differs from short-term repeatability.

DefinitionMeasurementMaximum permissible error and accuracy class

A specification limit is not an uncertainty estimate.

DefinitionMeasurementDefinitional uncertainty

More repetitions do not resolve an underspecified measurand.

DefinitionMeasurementRelative standard uncertainty

Relative uncertainty uses a nonzero measured magnitude.

DefinitionMeasurementBlank indications and null measurement uncertainty

A zero or blank reading can still have uncertainty.

DefinitionMeasurementTarget measurement uncertainty

An intended-use target differs from achieved uncertainty.

DefinitionMeasurementIntermediate precision conditions

Within-location changed conditions differ from strict repeatability.

DefinitionMeasurementCommutability of a reference material

Certification alone does not establish equivalence across procedures.

DefinitionChemistrySubstances, elements, compounds and mixtures

Chemical composition and spatial uniformity describe different features of matter.

DefinitionChemistryPhysical change and chemical change

A change of phase need not change chemical identity.

DefinitionChemistryEmpirical, molecular and structural formulas

A formula's subscripts represent different information in different chemical models.

Definition
DefinitionSource checked

Relative standard uncertainty

Measurement

Relative uncertainty uses a nonzero measured magnitude.

Key knowledge

Relative standard uncertainty is standard uncertainty divided by the absolute measured quantity value. For y≠0, u_r=u(y)/|y|; its percentage form is100u_r%. Near zero, relative uncertainty can become arbitrarily large while absolute uncertainty remains finite. The scale’s zero must have the intended meaning: an offset temperature conversion changes relative ratios even when the same temperature is represented.

Values and equations

u_r=u(y)/|y|, y≠0; percentage=100u_r%

u_r
Relative standard uncertainty 1
u(y)
Standard uncertainty of y chosen quantity unit
y
Nonzero measured quantity value chosen quantity unit
percentage
Relative standard uncertainty expressed per hundred %

Conditions and scope

  • The numerator is a standard uncertainty with the same units as y, not an expanded uncertainty or a maximum error.
  • The ratio is undefined at y=0. For logarithmic, ordinal or offset scales, state the scale and interpret whether a relative ratio serves the measurement purpose.
Sources · 1

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. VIM3, entry 2.32JCGM — International Vocabulary of Metrology, 3rd edition (2012), annotated online editionReference guidejcgm.bipm.orgRead source

Evidence and review

Read VIM2.32 absolute-value quotient definition. The zero-domain, near-zero behavior and scale-offset caveats are disclosed algebraic consequences plus the already verified unit-conversion record, not additional VIM claims.

2026-10-10 · /root/audit_life_earth_chemistry — independent Chemistry/Life/Earth editor. Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.

Related reference entries

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Scientific relationships · 2 / 2

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Uses definition
    Relationship sources · 1

    Linked statements

    • Relative standard uncertainty is standard uncertainty divided by the absolute measured quantity value. For y≠0, u_r=u(y)/|y|; its percentage form is100u_r%. Near zero, relative uncertainty can become arbitrarily large while absolute uncertainty remains finite. The scale’s zero must have the intended meaning: an offset temperature conversion changes relative ratios even when the same temperature is represented.

    This relation concerns the stated relative standard uncertainty claim and its conditions; it does not assert an unqualified prerequisite or an additional theorem.

  2. Uses definition
    Relationship sources · 1

    Linked statements

    • Relative standard uncertainty is standard uncertainty divided by the absolute measured quantity value. For y≠0, u_r=u(y)/|y|; its percentage form is100u_r%. Near zero, relative uncertainty can become arbitrarily large while absolute uncertainty remains finite. The scale’s zero must have the intended meaning: an offset temperature conversion changes relative ratios even when the same temperature is represented.

    This relation concerns the stated relative standard uncertainty claim and its conditions; it does not assert an unqualified prerequisite or an additional theorem.

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