Overview
ISO 24477:2025 - "Vacuum technology - Vacuum gauges - Specifications, calibration and measurement uncertainties for spinning rotor gauges" provides standardized definitions, required specifications and calibration procedures for spinning rotor gauges (SRGs). Applicable up to 2 Pa, this second-edition International Standard clarifies terminology, lists essential instrument parameters, and defines how to evaluate and report measurement uncertainties for SRGs used in medium and high vacuum work.
Key topics and requirements
The standard addresses both component-level and metrological requirements for SRGs. Main technical topics include:
- Terms and definitions specific to SRGs (rotor, thimble, suspension head, controller, flange assembly).
- Physical parameters including the accommodation factor (σ) and effective accommodation factor (σeff), residual drag and offset (p_offs).
- Specifications for SRG hardware, such as rotor diameter and density, rotor and thimble materials, connecting flange, leak rate, suspension head positioning, limits of rotor frequency, warm-up and baking conditions, measurement range, sampling time and internal volume.
- Interface and environmental requirements: electrical input, display and signal outputs, nominal operating conditions, storage and transport conditions, and mechanical limits (vibration, dimensions, cable length).
- Calibration: parameters to calibrate, general calibration procedures and two calibration methods (A and B) for deriving effective accommodation factors, plus requirements for calibration uncertainty and calibration certificates.
- Measurement uncertainty at use: guidance on which uncertainty contributions to consider during routine operation and reporting.
Applications and users
ISO 24477:2025 is intended for organizations and professionals who design, calibrate or use spinning rotor gauges, including:
- Metrology and calibration laboratories performing SRG calibrations and uncertainty evaluations.
- Instrument manufacturers specifying SRG performance and producing calibration documentation.
- Research laboratories and industrial users in semiconductor processing, vacuum coating, surface science and other fields needing reliable medium/high vacuum pressure measurement.
- Quality and compliance teams requiring traceable SRG calibration and standardized reporting up to 2 Pa.
Related standards
ISO 24477:2025 complements and references other ISO documents for vacuum gauge calibration and uncertainty evaluation, notably:
- ISO 3567 - Calibration by direct comparison with a reference gauge
- ISO 27893 - Evaluation of uncertainties for calibrations by direct comparison
- Guides on uncertainty and vocabulary: ISO/IEC Guide 98‑3 (GUM) and ISO/IEC Guide 99 (VIM)
By standardizing terminology, specification limits and calibration methods, ISO 24477:2025 helps ensure consistent, traceable SRG performance and reliable vacuum pressure measurements across laboratories and industries.
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