CIE 220:2016 – Characterization and Calibration Method of UV Radiometers

This article gives a short overview of the history of the document CIE 220:2016 Characterization and Calibration Method of UV Radiometers (CIE, 2016) and its most important content. In particular, the subject of spectral mismatch is covered. The technical document CIE 220 prepared by CIE Technical Committee TC2-47 describes quality indices for UV radiometers, which enable manufacturers and users to characterize instruments on a common basis. To harmonize CIE documents, the quality indices described in this document relate to the quality indices described in Joint ISO/CIE International Standard ISO/CIE 19476:2014(E) (formerly CIE S 023/E:2013). All these considerations are important for the calibration and the use of UV radiometers. If every manufacturer would give the values mentioned in the CIE 220, the user will be able to correct his measurements and therefore obtain much better values comparable to UV radiometers from different manufacturers. History and success of the document The starting point of the CIE 220 was 18 years ago. A working group pursuing the work was established in the first workshop of the “Thematic Network for Ultraviolet Measurements” in Espoo, March 2 and 3, 1998. The network was funded by the Standards, Measurements and Testing program of the Commission of the European Communities, as project number SMT4-CT97-7510. Within the Working Group 1 “Guidance for UV power meter classification for particular applications,” chaired by Anton Gugg-Helminger, the document “Characterizing the Performance of Integral Measuring UV-Meters” was prepared. It was published in UV News in November 2000. [2] This publication was taken over to the CIE within the technical committee TC2-47 with chair Gan Xu in 2001. The new title was “Methods of Characterization and Calibration of Broad Band UV Radiometers.” In 2006, Armin Sperling became the new chair and finished this long process in 2016 with “Characterization and Calibration Methods of UV Radiometers.” From the initial idea through to the finished document, it has taken 18 years of work all around the world. The published document provides helpful guidance on the characterization of UV radiometers. To harmonize CIE documents, the quality indices described in CIE 220 relate to the quality indices described in Joint ISO/CIE International Standard ISO/CIE 19476:2014(E) (formerly CIE S 023/E:2013), and references are made to those where applicable. Unlike photometers, the subject of ISO/CIE 19476:2014(E), UV radiometers may be designed for various actinic spectra and different spectral ranges. Therefore, instead of only one defined spectral reference source (CIE Source A) used in ISO/CIE 19476:2014(E) three reference spectra as shown in Figures 1 and 2 are proposed in CIE 220 to support the generic spectral characterization of UV radiometers for various applications. Spectral mismatch evaluation Spectral mismatch is a major uncertainty source, maybe the largest one, hence one of the most important characterization parameters of a UV radiometer. After the first publication in 2000, Gigahertz-Optik GmbH started to measure the relative spectral responsivity of each broadband UV radiometer that was delivered, and it is possibly still the only manufacturer doing so. With this knowledge, every customer is able to calculate the spectral mismatch a(Z) value. The application of this a(Z) value is a key parameter for precise measurements. It allows correction of the measured value, corresponding to the calibration source and not to the actual source measured. In CIE 220, the a(Z) value is called aact,R,Z, the spectral mismatch. The spectral mismatch aact,R,Z is defined as the ratio of the effective responsivity of the meter head with respect to the radiant quantity of the test source sact,Z, to the effective responsivity with respect to the reference source sact,R as * *