Pyranometer Calibration Methods Explained: ISO 9847 vs. ISO 9060
Understanding Pyranometer Calibration Standards
Pyranometers are precision instruments designed to measure solar irradiance—the power of sunlight received per unit area. For reliable performance, these sensors must be calibrated according to international standards that define how accuracy and consistency are maintained across instruments and laboratories.
Two of the most recognized standards for pyranometer calibration are ISO 9847 and ISO 9060. Although they are closely related, they serve different purposes within the calibration and classification process.
ISO 9847: Calibration by Comparison to a Reference Pyranometer
ISO 9847 describes the standard method for calibrating a field pyranometer by comparison to a reference pyranometer under natural sunlight conditions.
Key Points:
- The test is performed outdoors using simultaneous measurements from the pyranometer under test and a calibrated reference instrument.
- The reference pyranometer must have a traceable calibration—usually linked to a World Radiometric Reference (WRR) or ISO 17025-accredited laboratory.
- Calibration involves statistical comparison of outputs over varying solar intensities and zenith angles.
Advantages:
- Represents real-world conditions (natural sunlight, atmospheric effects, and spectral distribution).
- Cost-effective and widely used by calibration labs and field technicians.
Limitations:
- Accuracy can be affected by weather variability, such as clouds, wind, or temperature fluctuations.
- Requires stable sunlight and clear sky conditions for valid results.
ISO 9060: Pyranometer Classification and Performance Standards
While ISO 9847 focuses on calibration procedure, ISO 9060 defines performance criteria and classification for pyranometers based on their precision, stability, and response characteristics.
Key Points:
- Introduces categories like Class A (Secondary Standard), Class B (First Class), and Class C (Second Class) pyranometers.
- Specifies parameters such as:
- Response time
- Temperature dependence
- Linearity
- Directional and spectral response
- Zero offset due to thermal radiation or ambient temperature changes
- Defines performance thresholds each class must meet.
Advantages:
- Provides a universal benchmark for comparing sensor performance.
- Ensures consistent quality across manufacturers and laboratories.
Limitations:
- Does not provide a step-by-step calibration procedure.
- Must be used alongside ISO 9847 or similar standards for complete calibration traceability.
ISO 9847 vs. ISO 9060: The Key Differences
| Feature | ISO 9847 | ISO 9060 |
|---|---|---|
| Purpose | Defines the calibration method for pyranometers | Defines classification and performance requirements |
| Focus | Field comparison calibration | Instrument performance and accuracy standards |
| Output | Calibration factor (correction coefficient) | Instrument class (A, B, or C) |
| Environment | Outdoor (natural sunlight) | Laboratory or specification-based |
| Primary Use | Calibration labs, field testing | Manufacturers, equipment selection |
In short, ISO 9847 tells you how to calibrate, while ISO 9060 tells you how good a pyranometer needs to be.
Why Both Standards Matter
Together, these standards ensure pyranometers deliver traceable, reliable solar radiation data. Whether for solar energy assessment, meteorological research, or agricultural monitoring, calibration ensures:
- Comparable results across instruments.
- Compliance with international measurement standards.
- Confidence in long-term irradiance data.
Calibration with ISOCAL North America
At ISOCAL North America, we perform pyranometer calibration according to ISO 9847 and ISO 17025 standards, ensuring results that are traceable, repeatable, and globally recognized. Our team works with pyranometers from all major manufacturers and offers:
- Outdoor and laboratory calibration options
- Traceability to World Radiometric Reference (WRR)
- Fast turnaround times
- Detailed calibration certificates with uncertainty values
Conclusion
For any application relying on solar irradiance data, proper calibration is essential. ISO 9847 ensures your pyranometer is accurately calibrated under real-world conditions, while ISO 9060 verifies that your instrument meets the performance requirements of its class.
By adhering to both standards, ISOCAL North America guarantees the highest accuracy and consistency in your pyranometer measurements—supporting the reliability of your research, monitoring, and solar energy projects.
