This part of IEC 60904 sets the requirements for calibration procedures intended to establish the traceability of photovoltaic (PV) reference devices to SI units as required by IEC 60904-2. This standard applies to PV reference devices that are used to measure the irradiance of natural or simulated sunlight for the purpose of quantifying the performance of PV devices. The use of a PV reference device is required in the application of 60904-1 and 60904-3. This standard has been written with single-junction PV reference devices in mind, in particular crystalline Silicon. However, the main part of the standard is sufficiently general to include other single-junction technologies.