Overview
ISO 20146:2019 - "Vacuum technology - Vacuum gauges - Specifications, calibration and measurement uncertainties for capacitance diaphragm gauges" - provides standardized guidance for using and characterizing capacitance diaphragm gauges (CDGs). The standard defines terms, lists required specifications for CDGs, describes a calibration procedure, and identifies the measurement uncertainties to consider when CDGs are used as field or reference instruments. ISO 20146 complements ISO 3567 and ISO 27893 and is intended for the dissemination of pressure scales from medium vacuum up to atmospheric pressure.
Key Topics
- Definitions and terminology for CDG components and modes (measurement side, reference side, absolute vs differential CDGs, integrated type).
- Required specifications to be supplied for any CDG, including: measurement range, expected measurement uncertainty, resolution, response time, warm-up period, admissible and burst pressures, materials exposed to gas, mounting orientation, internal volume, interfaces and connections, environmental and storage conditions, and power requirements.
- Additional (optional) specifications such as reproducibility (long‑term instability), tilting effects, repeatability of zero, durability after overloads, update interval, connector and cable details, and inspection/calibration records.
- Calibration guidance that aligns with ISO 3567 and ISO 27893: procedures for direct comparison calibration, calibration certificate content, and reporting of calibration uncertainty.
- Measurement uncertainty at use: methods to evaluate and report uncertainties during normal operation, with reference to GUM principles (ISO/IEC Guide 98‑3).
- Special topics: thermal transpiration compensation (informative Annex A) and how to treat effects specific to vacuum measurements.
Applications
ISO 20146 is practical for:
- Calibration laboratories establishing CDGs as reference standards or performing routine calibrations.
- Instrument manufacturers specifying performance data and compliance for CDG products.
- Vacuum system designers and process engineers selecting gauges for research, semiconductor fabrication, thin‑film deposition, and other vacuum processes.
- Metrologists and quality managers building uncertainty budgets and traceable measurement chains for pressure measurement from medium vacuum to atmosphere.
Related Standards
- ISO 3567 - Calibration by direct comparison with a reference gauge
- ISO 27893 - Evaluation of uncertainties for calibrations by direct comparison
- ISO 3529 parts 1 & 3 - Vacuum technology vocabulary
- ISO/IEC Guide 98‑3 (GUM) and ISO/IEC Guide 99 (VIM) - measurement uncertainty and metrology terms
By following ISO 20146:2019, organizations ensure consistent specification, calibration, and uncertainty evaluation of capacitance diaphragm gauges, supporting traceable and reliable vacuum pressure measurement.
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