SIST EN ISO 6145-7:2019/A1:2026

• Status: Not Published
• Public Enquiry End Date: 29-Jan-2026
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: DPL - Gas supply
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 09-Nov-2026
• Due Date: 14-Jan-2027
• Ref Project: EN ISO 6145-7:2018/A1:2026 - Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7: Thermal mass-flow controllers - Amendment 1: Correction of Formula C.4 (ISO 6145-7:2018/Amd 1:2026)

• Referred By: SIST EN ISO 23581:2024 - Petroleum products and related products - Determination of kinematic viscosity - Method by Stabinger type viscometer (ISO 23581:2024)
• Effective Date: 28-Jan-2026
• Amends: SIST EN ISO 6145-7:2019 - Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7: Thermal mass-flow controllers (ISO 6145-7:2018)
• Effective Date: 01-Dec-2026

SIST EN ISO 6145-7:2019/A1:2026 is the Slovenian adoption of the ISO amendment to Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7: Thermal mass-flow controllers. It corrects Annex C in the base standard, including Formula C.4, so users applying the uncertainty calculation in this part use the revised expression. The document is published by SIST and is identified as identical to EN ISO 6145-7:2018/prA1.

What does SIST EN ISO 6145-7:2019/A1:2026 specify?

SIST EN ISO 6145-7:2019/A1:2026 specifies amendments to the thermal mass-flow controller part of the ISO 6145 series for preparing calibration gas mixtures by dynamic methods. In practice, it is a correction document: it updates selected text and the uncertainty formula in Annex C rather than setting out a full standalone method.

The amendment is organized around three edits:

• the paragraph following Figure 3
• the titles of C.1 and C.2
• Formula C.4 and the expressions that follow it

Annex C is the part affected by the technical correction. That matters because users who calculate uncertainty from this annex need the exact corrected wording and formula set, not the earlier version.

What are the key requirements of SIST EN ISO 6145-7:2019/A1:2026?

SIST EN ISO 6145-7:2019/A1:2026 corrects the text used with the uncertainty calculation in Annex C. The main practical point is that anyone using the Annex C method for thermal mass-flow controller work should apply the amended wording and formula sequence exactly as published.

Text corrections after Figure 3

SIST EN ISO 6145-7:2019/A1:2026 replaces the percentage expressions after Figure 3 by removing the plus-minus signs. In practical terms, this is a wording correction that affects how the tolerance-style values are read in the surrounding text.

Titles of C.1 and C.2

SIST EN ISO 6145-7:2019/A1:2026 corrects the symbol used in the titles of C.1 and C.2. This matters because the annex headings identify the uncertainty cases covered in the calculation section, so the corrected symbol keeps the notation consistent with the formulas.

Formula C.4

SIST EN ISO 6145-7:2019/A1:2026 replaces Formula C.4 and the formulas that follow it with a corrected uncertainty expression and derivation. In practice, this is the core technical change: users who evaluate relative standard uncertainty in Annex C must use the revised equation chain, not the earlier one.

Derivation by differentiation

SIST EN ISO 6145-7:2019/A1:2026 keeps the explanation that the result comes from differentiating Formula C.3 and substituting into Formula C.4. That tells the reader the corrected expression is not a new method, but a corrected mathematical development of the existing method.

Relative standard uncertainty

SIST EN ISO 6145-7:2019/A1:2026 presents the relative standard uncertainty of ϕA as the outcome of the corrected calculation. For users, this means the annex is meant for uncertainty budgeting in calibration gas mixture preparation, not for a general gas-analysis classification.

What terms does SIST EN ISO 6145-7:2019/A1:2026 define?

SIST EN ISO 6145-7:2019/A1:2026 uses a small set of technical terms that frame the amendment.

• Thermal mass-flow controllers - devices used to control gas flow based on thermal measurement principles; they are the subject of Part 7.
• Calibration gas mixtures - gas mixtures prepared for calibration work, where the mixture composition must be controlled and traceable.
• Dynamic methods - preparation methods that create gas mixtures by controlled flows rather than by static blending.
• Relative standard uncertainty - the uncertainty measure used in Annex C to express the calculation result in relative form.
• Nominally pure gases - gases treated as essentially pure for the specific uncertainty case in C.1.
• Diluting a gas mixture - the second uncertainty case in C.2, where an existing mixture is diluted before use.

Who uses SIST EN ISO 6145-7:2019/A1:2026?

SIST EN ISO 6145-7:2019/A1:2026 is used by laboratories and organizations that prepare calibration gas mixtures with dynamic methods. That includes gas-analysis laboratories, calibration laboratories, and technical staff responsible for uncertainty calculations on gas mixture preparation equipment.

It is also relevant to manufacturers and users of thermal mass-flow controllers, because the corrected annex affects the calculation basis used when specifying, checking, or documenting mixture preparation performance. Quality managers and buyers use it when they need to verify that a calibration process is aligned with the corrected ISO wording.

What changed in SIST EN ISO 6145-7:2019/A1:2026 from the previous edition?

SIST EN ISO 6145-7:2019/A1:2026 is an amendment to ISO 6145-7:2018. The changes stated in the document are limited to:

• a correction in the paragraph following Figure 3
• corrections to the titles of C.1 and C.2
• a replacement of Formula C.4 and the following derivation

What does the SIST EN ISO 6145-7:2019/A1:2026 document contain?

SIST EN ISO 6145-7:2019/A1:2026 contains amendment text only, focused on corrections in Annex C. The document shows the revised wording around Figure 3 and the corrected labels for the two uncertainty cases in C.1 and C.2.

It also provides the corrected Formula C.4 and the subsequent symbolic derivation used to obtain the relative standard uncertainty expression. For engineers and laboratories, that means the document is mainly a calculation correction for design, test, and uncertainty documentation work rather than a broad-method standard.

SLOVENSKI STANDARD
SIST EN ISO 6145-7:2019/oprA1:2026
01-januar-2026
Analiza plinov - Priprava kalibracijskih plinskih zmesi z uporabo dinamičnih metod
- 7. del: Termični regulatorji masnega pretoka - Dopolnilo A1: Popravek enačbe
(C.4) (ISO 6145-7:2018/DAM 1:2025)
Gas analysis - Preparation of calibration gas mixtures using dynamic methods - Part 7:
Thermal mass-flow controllers - Amendment 1: Correction of formula C.4 (ISO 6145-
7:2018/DAM 1:2025)
Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamischen
Verfahren - Teil 7: Thermische Massendurchflussregler – Änderung 1: Berichtigung der
Gleichung (C.4) (ISO 6145-7:2018/DAM 1:2025)
Analyse des gaz - Préparation des mélanges de gaz pour étalonnage à l'aide de
méthodes dynamiques - Partie 7: Régulateurs thermiques de débit massique -
Amendement 1: Correction de la Formule C.4 (ISO 6145-7:2018/DAM 1:2025)
Ta slovenski standard je istoveten z: EN ISO 6145-7:2018/prA1
ICS:
71.040.40 Kemijska analiza Chemical analysis
SIST EN ISO 6145-7:2019/oprA1:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

SIST EN ISO 6145-7:2019/oprA1:2026

SIST EN ISO 6145-7:2019/oprA1:2026
DRAFT
Amendment
ISO 6145-7:2018/
DAM 1
ISO/TC 158
Gas analysis — Preparation of
Secretariat: SAC
calibration gas mixtures using
dynamic methods —
Voting begins on:
2025-11-10
Part 7:
Voting terminates on:
Thermal mass-flow controllers 2026-02-02
AMENDMENT 1: Correction of formula
C.4
ICS: 71.040.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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ISO/CEN PARALLEL PROCESSING
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POTENTIAL TO BECOME STANDARDS TO
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RECIPIENTS OF THIS DRAFT ARE INVITED
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Reference number
ISO 6145-7:2018/DAM 1:2025(en)

SIST EN ISO 6145-7:2019/oprA1:2026
DRAFT
ISO 6145-7:2018/DAM 1:2025(en)
Amendment
ISO 6145-7:2018/
DAM 1
ISO/TC 158
Gas analysis — Preparation of
Secretariat: SAC
calibration gas mixtures using
dynamic methods —
Voting begins on:
Part 7:
Voting terminates on:
Thermal mass-flow controllers
AMENDMENT 1: Correction of
formula C.4
ICS: 71.040.40
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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TO SUBMIT, WITH THEIR COMMENTS,
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NOTIFICATION OF ANY RELEVANT PATENT
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Published in Switzerland Reference number
ISO 6145-7:2018/DAM 1:2025(en)

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SIST EN ISO 6145-7:2019/oprA1:2026
ISO 6145-7:2018/DAM 1:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical comm
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