The Impact of Indoor and Outdoor Radiometer Calibration on Solar Measurements

Research output: NRELPoster


This study addresses the effect of calibration methodologies on calibration responsivities and the resulting impact on radiometric measurements. The calibration responsivities used in this study are provided by NREL's broadband outdoor radiometer calibration (BORCAL) and a few prominent manufacturers. The BORCAL method provides outdoor calibration responsivity of pyranometers and pyrheliometers at a 45 degree solar zenith angle and responsivity as a function of solar zenith angle determined by clear-sky comparisons to reference irradiance. The BORCAL method also employs a thermal offset correction to the calibration responsivity of single-black thermopile detectors used in pyranometers. Indoor calibrations of radiometers by their manufacturers are performed using a stable artificial light source in a side-by-side comparison of the test radiometer under calibration to a reference radiometer of the same type. These different methods of calibration demonstrated 1percent to 2 percent differences in solar irradiance measurement. Analyzing these values will ultimately enable a reduction in radiometric measurement uncertainties and assist in developing consensus on a standard for calibration.
Original languageAmerican English
StatePublished - 2016

Publication series

NamePresented at the European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC), 20-24 June 2016, Munich, Germany

NREL Publication Number

  • NREL/PO-5D00-66668


  • broadband outdoor radiometer calibration
  • calibration
  • pyranometers
  • radiometric measurements


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