ISO 9847:2023

Overview

ISO 9847:2023 - "Solar energy - Calibration of pyranometers by comparison to a reference pyranometer" specifies standardized methods to calibrate pyranometers used to measure hemispherical solar irradiance. The standard defines two preferred comparison-based approaches: indoor (Type A) calibrations against lamp sources and outdoor (Type B) calibrations using natural solar radiation. Calibration results are reported as an instrument sensitivity with an associated uncertainty, and procedures are designed to be SI-traceable via the World Radiometric Reference (WRR) when traceable reference instruments are used.

Keywords: ISO 9847:2023, pyranometer calibration, solar energy, SI traceability, WRR, sensitivity, uncertainty evaluation

Key topics and technical requirements

• Calibration methods
  • Type A (Indoor)
    • A1: Direct-beam lamp source at normal incidence (receiver perpendicular to beam)
    • A2: Uniform diffuse lamp source using an integrating sphere
  • Type B (Outdoor)
    • B1: Horizontal position (global horizontal irradiance, GHI)
    • B2: Tilted position (inclined plane)
    • B3: Normal incidence (tracking to sun)
• Traceability and reference standards
  • Calibrations are traceable to SI through the World Radiometric Reference (WRR) (WRR uncertainty < ±0.3%), provided traceable reference pyranometers are used.
• Instrument applicability
  • Applicable to most pyranometer technologies and validated for pyranometers meeting classes A, B and C of ISO 9060.
  • Spectrally flat vs non‑spectrally flat: non‑spectrally flat instruments may have wavelength-dependent response (300–1 500 nm) and calibration may be valid under more limited conditions.
• Measurement and uncertainty
  • Calibration yields a single sensitivity (for most linear-output pyranometers) plus an uncertainty. Annexes provide guidance and example calculations for uncertainty evaluation (referencing ISO/IEC Guide 98-3 and other practices).

Practical applications and users

• Calibration procedures in ISO 9847:2023 support activities requiring low measurement uncertainty:
  • Solar resource assessment and mapping
  • Performance testing and monitoring of PV and solar-thermal power plants
  • Meteorological services and climate monitoring stations
  • Instrument manufacturers and calibration laboratories
  • Building energy modeling, agriculture, materials testing
• Users: calibration labs, national metrology institutes, solar‑plant operators, research centres, instrument manufacturers and quality managers implementing ISO 9060-compliant measurement systems.

Related standards

• ISO 9060 - Specification and classification of pyranometers (classes A, B, C)
• ISO/IEC Guide 98-3 (GUM) - Guide to the expression of measurement uncertainty
• World Radiometric Reference (WRR) - SI reference for irradiance

ISO 9847:2023 provides practical, validated procedures for reliable, traceable pyranometer calibration to support high-quality solar irradiance measurements across research, industry and operations.