IEC 60904-4:2019 pdf download – Photovoltaic devices – Part 4: Photovoltaic reference devices – Procedures for establishing calibration traceability.
3.6 traceability <of a PV reference device> requirement for any PV reference device, to tie its calibration value to SI units in an unbroken and documented chain of calibration transfers including stated uncertainties Note 1 to entry: The WRR has been compared several times to the SI radiometric scale. While in previous comparisons the two scales were found to be indistinguishable within the uncertainty of the comparison, the latest comparison of scales established that there is a systematic shift between the scales, with WRR reading 0,34 % higher irradiance than the SI scale. The uncertainty of this shift was given as 0,1 8 % (k = 2). Therefore, traceability to WRR automatically provides traceability to SI units. However, the shift between the scales may be corrected for those measurements traceable to the WRR. The uncertainty of the scale comparison shall be included into the uncertainty budget. Essentially there are two possibilities for those measurements traceable to SI units via the WRR. Firstly, no correction is applied for the scale difference and a larger uncertainty of 0,3 % (rectangular distribution) shall be used. Secondly an explicit correction of the scale difference amounting to 0,34 %. In this case the uncertainty contribution is 0,1 8 % (k = 2). The value of 0,34 % for the scale difference is the latest available at time of publication of this document. The scientific literature should be checked for possible updates of this difference and its uncertainty. In particular, it is possible that in the future the WRR is adapted to take account of this difference and bring it into line with SI units. In this case no further correction shall be applied. [SOURCE: A Fehlmann, G Kopp, W Schmutz, R Winkler, W Finsterle, N Fox, metrologia 49 (201 2) S34]
4 Requirements for traceable calibration procedures of PV reference devices A traceable calibration procedure is necessary to transfer calibration from a standard or reference measuring solar irradiance and based on a physical principle other than PV effect (such as cavity radiometer, pyrheliometer and pyranometer) to a PV reference device. The requirements for such procedures are as follows: a) Any measurement instrument required and used in the transfer procedure shall be an instrument with an unbroken traceability chain. b) A documented uncertainty analysis. c) Documented repeatability, such as measurement results of laboratory intercomparison, or documents of laboratory quality control. d) Inherent absolute accuracy, given by a limited number of intermediate transfers. Normally the transfer would be from a secondary standard to a PV reference device constituting a primary reference. The transfer from one PV reference device to another is covered by IEC 60904-2. 5 Uncertainty analysis An uncertainty estimate according to ISO/IEC Guide 98-3: 2008 shall be provided for each traceable calibration procedure. This estimate shall provide information on the uncertainty of the calibration procedure and quantitative data on the following uncertainty factors for each instrument used in performing the calibration procedure. In particular: a) Component of uncertainty arising from random effects (Type A). b) Component of uncertainty arising from systematic effects (Type B).
6 Calibration report The calibration report shall include at least the following information: a) title (e.g. ”Calibration Certificate”); b) name and address of laboratory, and location where the calibrations were carried out, if different from the address of the laboratory; c) unique identification of the report (such as serial number) and of each page, the total number of pages and the date of issue; d) name and address of the client placing the order; e) description and unambiguous identification of the item(s) calibrated; f) date of receipt of calibration item(s) and date(s) of performance of calibration, as appropriate; g) calibration results and their uncertainties, including the temperature of the device at which the calibration was performed; h) reference to sampling procedures used by the laboratory where these are relevant to the validity or application of the results; i) the name(s), title(s) and signature(s) or equivalent identification of person(s) authorizing the report; j) where relevant, a statement to the effect that the results relate only to the items calibrated; k) where relevant the spectral responsivity of the PV reference device; l) where relevant the temperature coefficient of the PV reference device. 7 Marking The calibrated PV reference device shall be marked with a serial number or reference number and the following information attached or provided on an accompanying certificate: a) date of (actual or present) calibration; b) calibration value and its uncertainty; c) identification of laboratory having performed the calibration.