ISO/IEC 17025 is the standard that calibration and testing laboratories are accredited against. Its requirements on equipment and metrological traceability (clauses 6.4 and 6.5) mean that every instrument that affects a reported result must be calibrated, with a documented, unbroken chain back to the SI. For PV power measurement, that applies to the solar simulator as a whole, not just to its reference cell.
Everything in the I-V chain must be calibratable
- Irradiance: the reference cell and the amplifier that reads it.
- Voltage and current: the measurement channels of the electronic load and acquisition.
- Temperature: the sensors on the device and on the reference cell.
- Spectrum: the data used for spectral-mismatch correction.
The electronic load is often the weak link
A load that can only be adjusted by its maker, or whose voltage and current channels cannot be checked against an external, traceable reference, cannot be brought into an accredited laboratory’s own calibration programme. The laboratory then cannot demonstrate traceability for the I-V curve itself, whatever the class of the light. Ask how the load is calibrated, against which reference, and whether the laboratory or its accredited calibration provider can do it independently.
How Pasan systems support accreditation
Pasan measurement chains are traceable to METAS, the Swiss federal metrology institute, under ISO/IEC 17025. The WPVS transimpedance amplifier reads non-shunted WPVS reference cells with ±0.1% accuracy, and Pasan systems are used by accredited laboratories, including Fraunhofer ISE, with Pasan’s reference simulators serving as the reference for more than 100 laboratories worldwide.
Questions to ask before you buy
- Can the voltage and current channels of the load be calibrated externally, by us or an accredited provider?
- Which traceable references are used, and are calibration factors recorded with every measurement?
- Is the reference cell read without a shunt, and how is its amplifier calibrated?
- Is there a documented uncertainty budget for Pmax that covers every term?
- Do accredited laboratories already use this system, and which ones?
See also how to check that a calibration certificate is genuine and how to read a solar simulator uncertainty budget.
Frequently asked questions
- What does ISO/IEC 17025 require of a solar simulator?
- Every instrument that affects a reported result must be calibrated with metrological traceability to the SI. For a solar simulator that includes the reference cell chain, the voltage and current channels of the electronic load, the temperature sensors and the spectral data.
- Why must the electronic load of a solar simulator be externally calibratable?
- Because an accredited laboratory has to demonstrate traceability for the I-V curve itself. If the load’s voltage and current channels cannot be checked against an external traceable reference, the laboratory cannot include them in its calibration programme.
- Are Pasan solar simulators used in ISO/IEC 17025 accredited laboratories?
- Yes. Pasan measurement chains are traceable to METAS under ISO/IEC 17025, accredited laboratories such as Fraunhofer ISE use Pasan systems, and Pasan reference simulators serve as the reference for more than 100 laboratories worldwide.
