ISO 6358-1:2013/FDAmd 2

FINAL DRAFT
Amendment
ISO 6358-1:2013/
FDAM 2
ISO/TC 131/SC 5
Pneumatic fluid power —
Secretariat: AFNOR
Determination of flow-rate
Voting begins on:
characteristics of components using
2026-01-26
compressible fluids —
Voting terminates on:
2026-03-23
Part 1:
General rules and test methods for
steady-state flow
AMENDMENT 2: Evaluation of
measurement uncertainty
Transmissions pneumatiques — Détermination des
caractéristiques de débit des composants traversés par un fluide
compressible —
Partie 1: Règles générales et méthodes d'essai en régime
stationnaire
AMENDEMENT 2: Évaluation de l'incertitude de mesure
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MADE IN NATIONAL REGULATIONS.
Reference number
ISO 6358-1:2013/FDAM 2:2026(en) © ISO 2026

FINAL DRAFT
ISO 6358-1:2013/FDAM 2:2026(en)
Amendment
ISO 6358-1:2013/
FDAM 2
ISO/TC 131/SC 5
Pneumatic fluid power —
Secretariat: AFNOR
Determination of flow-rate
Voting begins on:
characteristics of components using
compressible fluids —
Voting terminates on:
Part 1:
General rules and test methods for
steady-state flow
AMENDMENT 2: Evaluation of
measurement uncertainty
Transmissions pneumatiques — Détermination des
caractéristiques de débit des composants traversés par un fluide
compressible —
Partie 1: Règles générales et méthodes d'essai en régime
stationnaire
AMENDEMENT 2: Évaluation de l'incertitude de mesure
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
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BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
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TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
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MADE IN NATIONAL REGULATIONS.
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Published in Switzerland Reference number
ISO 6358-1:2013/FDAM 2:2026(en) © ISO 2026

ii
ISO 6358-1:2013/FDAM 2:2026(en)
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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has been established has the right to be represented on that committee. International organizations,
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
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This document was prepared by Technical Committee ISO/TC 131, Fluid power systems, Subcommittee SC 5,
Control products and components.
A list of all parts in the ISO 6358 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iii
ISO 6358-1:2013/FDAM 2:2026(en)
Pneumatic fluid power — Determination of flow-rate
characteristics of components using compressible fluids —
Part 1:
General rules and test methods for steady-state flow
AMENDMENT 2: Evaluation of measurement uncertainty

Annex C
Replace Annex C to update the method of calculation of the measurement uncertainty of the sonic
conductance.
ISO 6358-1:2013/FDAM 2:2026(en)
Annex C
(informative)
Evaluation of measurement uncertainty
C.1 General
The ISO Guide on uncertainty in measurement [ISO/IEC Guide 98-3:2008 (GUM:1995)] provides the
current international consensus method for estimating measurement uncertainty. There are different
ways to estimate measurement uncertainty; the strict mathematical way is described most extensively in
ISO/IEC Guide 98-3, but the other pragmatic methods that are compliant with ISO/IEC Guide 98-3 can be
used. The main rule appears as follows: effort and expenditure for determination of uncertainties are clearly
guided by the principle “fit for purpose”, i.e. effort and expenditure for determination of uncertainties are up
to standards to meet the requirements set by the user of the measurement data, but it is not over qualitative
in light of the application. This annex uses this principle.
ISO/IEC Guide 98-3 groups uncertainty components into Type A and Type B according to the way data
were obtained. Type A components are calculated by statistical means from repeated measurements, while
Type B components are taken from other sources, e.g. reference material, calibration certificates, accepted
values of constants, resolution, instability, environmental conditions.
In practice, however, a combined approach is most of the time considered as the most suitable. This combined
approach will apply very often, as each uncertainty cannot be estimated individually. In this case, Type B
will be used with reference materials and quality control materials to avoid some systematic measuring
error. The single uncertainties are combined applying th
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