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

• Status: Not Published
• Public Enquiry End Date: 29-Jan-2026
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: DPL - Gas supply
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 13-Nov-2025
• Due Date: 02-Apr-2026
• Completion Date: 12-Feb-2026
• 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
• Revises: 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-Jan-2026

SIST EN ISO 6145-7:2019/oprA1:2026 is a CEN amendment to the gas-analysis standard on preparing calibration gas mixtures using dynamic methods, Part 7 on thermal mass-flow controllers. It corrects the text and equations used in the Annex C uncertainty treatment, so laboratories and others who prepare or verify calibration gas mixtures can use the amended formula and wording.

What does SIST EN ISO 6145-7:2019/oprA1:2026 specify?

SIST EN ISO 6145-7:2019/oprA1:2026 specifies corrections to EN ISO 6145-7:2018 rather than a new preparation method. The amendment updates the paragraph after Figure 3, the titles of C.1 and C.2, and Formula C.4 and the formulas that follow in Annex C.

In practical terms, the document tells users of Part 7 to apply the corrected wording and uncertainty expression when working with thermal mass-flow controllers.

What are the key requirements of SIST EN ISO 6145-7:2019/oprA1:2026?

The amendment is mainly about using the corrected mathematical and textual references in Part 7.

• Paragraph after Figure 3 - SIST EN ISO 6145-7:2019/oprA1:2026 replaces “±10 %” with “10 %” and “±9 %” with “9 %”. In practice, readers should use the amended wording exactly as published when citing those percentage values.

• Titles C.1 and C.2 - SIST EN ISO 6145-7:2019/oprA1:2026 corrects the notation in the Annex C subsection titles. This matters because the same symbol is used in the uncertainty discussion, so the headings and the equations stay aligned.

• Formula C.4 - SIST EN ISO 6145-7:2019/oprA1:2026 replaces Formula C.4 and the formulas that follow it. In practice, anyone calculating uncertainty for calibration gas preparation by this method should use the corrected propagation formula, not the earlier version.

• Derivation from Formula C.3 - SIST EN ISO 6145-7:2019/oprA1:2026 states that the updated expression comes from differentiation of Formula C.3 and substitution into Formula C.4. That tells users how the uncertainty result is built up, which is important when checking a calculation or audit trail.

• Relative standard uncertainty in Annex C - SIST EN ISO 6145-7:2019/oprA1:2026 keeps the focus on relative standard uncertainty for the quantity identified in Annex C. In practice, this is the part a laboratory uses when it documents the uncertainty budget for a calibration gas mixture.

• Two calculation cases in Annex C - SIST EN ISO 6145-7:2019/oprA1:2026 distinguishes the uncertainty case for nominally pure gases from the case for diluting a gas mixture. This helps the user choose the right calculation path for the preparation route actually used.

What terms does SIST EN ISO 6145-7:2019/oprA1:2026 define?

• Calibration gas mixtures - Gas mixtures prepared for calibration work, so instruments can be checked against a known composition.

• Dynamic methods - Preparation methods that combine and control gas flows during making the mixture, rather than relying only on static mixing.

• Thermal mass-flow controllers - Devices that regulate gas flow using thermal mass-flow measurement, which is the subject of Part 7.

• Relative standard uncertainty - The uncertainty of a quantity expressed relative to that quantity, used here for the Annex C calculations.

• Nominally pure gases - Gases treated as essentially pure for the uncertainty case in C.1.

• Diluting a gas mixture - The case in C.2 where an existing gas mixture is diluted before use.

Who uses SIST EN ISO 6145-7:2019/oprA1:2026?

SIST EN ISO 6145-7:2019/oprA1:2026 is used by gas-analysis and calibration laboratories, manufacturers and users of thermal mass-flow controllers, and technical staff who prepare calibration gas mixtures. It is also relevant to quality managers and buyers who need to specify how mixtures are prepared and how the uncertainty is documented.

Typical tasks include:

• preparing calibration gas mixtures by dynamic methods
• updating uncertainty calculations in technical records
• checking that a gas-mixing system follows the corrected Annex C expression
• documenting how a mixture was prepared for quality or audit purposes

What changed in SIST EN ISO 6145-7:2019/oprA1:2026 from the previous edition?

SIST EN ISO 6145-7:2019/oprA1:2026 is Amendment 1 to EN ISO 6145-7:2018. It makes three stated corrections:

• the wording after Figure 3
• the titles of C.1 and C.2
• Formula C.4 and the formulas that follow it

What does the SIST EN ISO 6145-7:2019/oprA1:2026 document contain?

SIST EN ISO 6145-7:2019/oprA1:2026 contains a short set of amendments rather than a full technical method. It gives the corrected wording after Figure 3 and the corrected titles for the two Annex C uncertainty cases.

It also replaces Formula C.4 and the subsequent derivation, so the amended calculation can be used in uncertainty work for calibration gas mixtures prepared with thermal mass-flow controllers.

The document is therefore a reference for editing, calculation, and technical documentation, especially where Annex C is used to support an uncertainty budget.

SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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
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Reference number
ISO 6145-7:2018/DAM 1:2025(en)

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
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Published in Switzerland Reference number
ISO 6145-7:2018/DAM 1:2025(en)

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ISO 6145-7:2018/DAM 1:2025(en)
Foreword
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