ISO 24477:2022

INTERNATIONAL ISO
STANDARD 24477
First edition
2022-08
Vacuum technology — Vacuum
gauges — Specifications, calibration
and measurement uncertainties for
spinning rotor gauges
Technique du vide — Manomètres à vide — Spécifications, étalonnage
et incertitudes de mesure pour manomètres à rotor
Reference number
ISO 24477:2022(E)
© ISO 2022

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ISO 24477:2022(E)
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© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO 24477:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 S c op e . 1
2 N ormative references . 1
3 T erms and definitions . 1
3.1 Terms related to components . . 2
3.2 T erms related to physical parameters . 2
4 S ymbols and abbreviated terms.4
5 P rinciple of a spinning rotor gauge . .4
6 S pecifications for spinning rotor gauge . 5
6.1 D iameter and density of rotor . 5
6.2 M aterials of rotor and thimble . 5
6.3 C onnecting flange of thimble . 5
6.4 L eak rate of thimble with flange . 5
6.5 Suspension head positioning . 5
6.6 L imits of rotor frequency . 6
6.7 W arm-up period . 6
6.8 B aking temperature . 6
6.9 M easurement range . 6
6.10 S ampling time . 6
6.11 I nternal volume . 6
6.12 I nterface and pin connections of controller . 6
6.13 D imensions and weights of suspension head and controller . 6
6.14 D isplay and signal output . 6
6.15 N ominal operating (environment) conditions. 6
6.16 S torage and transportation conditions . 6
6.17 I nput power and electrical requirements . 6
7 Ad ditional (optional) specifications for spinning rotor gauge . 7
7.1 L ong-term instability . 7
7.2 E xpected measurement uncertainty . 7
7.3 C ompatibility between a suspension head and a rotor . 7
7.4 I nspection record and calibration certificate . 7
7.5 A llowed vibration level . 7
7.6 C able length . 7
7.7 Photograph . . 7
8 C alibration .7
8.1 P arameters to be calibrated . 7
8.2 Calibration procedures . 8
8.2.1 General . 8
8.2.2 C alibration method A for σ . . 8
eff,0
8.2.3 Calibration method B for σ . 8
eff,0
8.3 C alibration uncertainty . 9
8.4 C alibration certificate . 9
9 M easurement uncertainty at use .10
Bibliography .11
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ISO 24477:2022(E)
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
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This document was prepared by Technical Committee ISO/TC 112, Vacuum technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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ISO 24477:2022(E)
Introduction
This document complements ISO 3567 and ISO 27893 when characterizing, calibrating or using
spinning rotor gauges (SRGs) as reference gauges.
SRGs are used to measure pressure in the high and medium vacuum. For the dissemination of the
pressure scale and measurement of high and medium vacuum pressures by this gauge, the relevant
parameters, calibration guidelines and uncertainties should be given, which are described in this
document.
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INTERNATIONAL STANDARD ISO 24477:2022(E)
Vacuum technology — Vacuum gauges — Specifications,
calibration and measurement uncertainties for spinning
rotor gauges
1 S cope
This document defines terms related to spinning rotor gauges (SRGs), specifies the necessary parameters
for SRGs, details their calibration procedure and describes which measurement uncertainties to
consider when operating these gauges. This document is applicable to pressure up to 2 Pa.
2 Normat ive references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3529-1, Vacuum technology — Vocabulary — Part 1: General terms
ISO 3529-3, Vacuum technology — Vocabulary — Part 3: Total and partial pressure vacuum gauges
ISO 3567, Vacuum gauges — Calibration by direct comparison with a reference gauge
ISO 27893, Vacuum technology — Vacuum gauges — Evaluation of the uncertainties of results of
calibrations by direct comparison with a reference gauge
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM: 1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
IEC 60050-300, International Electrotechnical Vocabulary - Electrical and electronic measurements and
measuring instruments - Part 311: General terms relating to measurements - Part 312: General terms
relating to electrical measurements - Part 313: Types of electrical measuring instruments - Part 314:
Specific terms according to the type of instrument
3 T erms and definitions
For the purposes of this document the terms and definitions given in ISO 3529-1, ISO 3529-3, ISO 3567,
ISO 27893, ISO/IEC Guide 98-3, ISO/IEC Guide 99, IEC 60050-300 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
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ISO 24477:2022(E)
3.1 Terms related to components
3.1.1
rotor
rotating element, which is magnetically suspended in vacuum
Note 1 to entry: As rotor any magnetic element can be used. For practical reasons, however, only spheres as
rotating element are considered in this document. A spherical rotor may exhibit a dipole magnetic field, but also
higher orders.
3.1.2
thimble
finger
tube in which the rotor (3.1.1) is magnetically suspended
Note 1 to entry: Material of the thimble is preferably non-magnetic stainless steel.
Note 2 to entry: Materials with high electrical conductivity are not suitable.
3.1.3
suspension head
measuring head
sensing head
device to be mounted on the thimble (3.1.2) that suspends, stabilizes, and accelerates the rotor (3.1.1)
under vacuum and detects the signal synchronous with the magnetic signal from the rotor
3.1.4
controller
device which controls the suspension head (3.1.3), indicates the deceleration
rate of the rotor (3.1.1) and the corresponding pressure with the help of setup parameters such as rotor
diameter, rotor density, gas species, temperature and effective accommodation factor
3.1.5
flange assembly
projecting flat rim with thimble (3.1.2), mounting rails, clamp and retaining screw for suspension head
(3.1.3), to be mounted to the vacuum vessel
3.2 T erms related to physical parameters
3.2.1
accommodation factor
σ
parameter which under molecular conditions is proportional to the tangential-momentum
accommodation coefficient of gas molecules hitting the rotor surface
Note 1 to entry: If the rotor is an ideal sphere, the surface is perfectly smooth and the values of diameter and
density of the rotor are exactly known, the accommodation factor is equal to the tangential-momentum
accommodation coefficient. This is provided that the mean-free path of the gas molecules is much greater than
the diameter of the thimble. In this case, the accommodation factor is lower or equal to 1. In the case of rough
rotors, however, σ might be higher than 1. σ is determined by calibration for an individual rotor, taking into
account surface roughness.
Note 2 to entry: In some literature, accommodation coefficient is used to represent the same meaning as the
accommodation factor defined herein.
Note 3 to entry: At pressures below 30 mPa, the accommodation factor is independent of pressure.
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