Influence of the light spectral distribution used in the radiometers calibration

The use of radiometers is common as a form of control in tests that engage exposure to natural or artificial electromagnetic radiation. The photodiode is a very much used device, capable of converting the incident radiation into electrical current, which is transformed in irradiance by a duly calibrated meter. The calibration of radiometers is made by comparing it with a spectroradiometer and a calibration factor is obtained. Considering that the photodiodes responsiveness is not constant for all wavelengths, the spectral distribution of the light source is a great influence factor in the calibration. Thus, the objective of this work was to evaluate the variation in the calibration factor of the radiometers resulting from the spectral distribution variation of the light source used. The results showed a variation of up to 16% in the calibration factor, reinforcing the importance of calibrating the radiometers with the same light source type used daily, in order to assure the accuracy of the measurements made with this type of equipment.