EKS-HUM-025 / Condensation, measurement and control

Measurement Uncertainty

测量不确定度

Measurement uncertainty is a non-negative parameter that characterises the dispersion of quantity values attributed to a measurand from the information used.

Aliases: uncertainty of measurement

QUANTITY, SYMBOL AND UNIT

Quantity / objectMeasurement uncertainty

Symbolu, U

UnitNot applicable

Definition

Measurement uncertainty is a non-negative parameter that characterises the dispersion of quantity values attributed to a measurand from the information used.

It belongs to a stated measurement result and measurement method. In humidity work, air temperature, RH, dew point and surface temperature can each have different uncertainty components that propagate into a condensation or control decision.

Relations and distinctions

Uncertainty and error

Measurement error is the difference from a reference value; uncertainty describes the dispersion associated with the value being attributed to the measurand.

Uncertainty and repeatability

Repeatability describes agreement under repeated conditions; uncertainty can also include calibration, resolution, drift, placement and other components.

Engineering meaning

Carry temperature and humidity uncertainty into derived dew point and surface comparisons.
Record the coverage basis, unit, measurand and conditions instead of reporting only an isolated plus/minus number.

Common misconceptions

MisconceptionA sensor accuracy specification is a complete measurement-uncertainty statement.

Accurate explanationA full result can also depend on calibration, resolution, drift, response, placement, sampling and the measurement model.

Application boundaries

Uncertainty does not automatically correct a known bias or an unsuitable measurement location.
Different uncertainty components should not be added without a defined propagation method and compatible coverage basis.

Supporting sources

Joint Committee for Guides in Metrology / SRC-JCGM-VIM-2-26

International Vocabulary of Metrology (VIM3), Entry 2.26: Measurement Uncertainty ↗

JCGM 200:2012, annotated online edition / VIM3 Entry 2.26 and Notes 1–4
Supports: Measurement uncertainty is a non-negative parameter characterising dispersion of values attributed to a measurand; Uncertainty is associated with a stated measured value and information used; Uncertainty can include Type A and Type B components
National Institute of Standards and Technology / SRC-NIST-HUMIDITY-CAL

Humidity Calibration Services at NIST ↗

Updated 2025-08-14 / Calibration-uncertainty section
Supports: Humidity calibration results have quantity-specific uncertainty; Dew/frost point and RH uncertainties are not interchangeable
ASHRAE / SRC-ASHRAE-41-6-2021-A

ANSI/ASHRAE Addendum a to ANSI/ASHRAE Standard 41.6-2021 - Standard Methods for Humidity Measurement ↗

Addendum a, 2022 / Public addendum and scope
Supports: Humidity measurement methods require defined procedures and reported conditions

Maintenance record