Irradiance is measured at a specified distance from the light source with a calibrated spectral radiometer. The spectrometer itself is calibrated in reference to a spectral irradiance standard which ensures the traceability of the calibration. The integral irradiance is calculated from the measured spectral data for the specified wavelength range. With the current lab irradiance standard lamps available, the spectral radiometer can be calibrated within the wavelength range from 250 to 2500 nm.
A factory calibration certificate is supplied listing the light source data, measurement set-up, traceability and calibration uncertainty.