Overview
ISO/TR 18486:2018 provides a calculation method to compare the spectral irradiance of a laboratory light source used for weathering tests with a reference solar spectral irradiance. It defines objective, reproducible parameters to quantify how well a solar simulator or other laboratory radiation source matches a reference “sun” over a chosen wavelength range, including the option to weight the comparison by a known action spectrum for a specific photochemical response.
Key Topics and Requirements
- Characterizing parameter f: A numerical metric that expresses the deviation between the laboratory source and the reference solar spectral irradiance. An ideal fit gives f = 0; larger values indicate worse fitting.
- Scaling conditions: Two scaling procedures are specified:
- Unweighted scaling by matching integrated spectral irradiance over a selected wavelength interval.
- Weighted scaling using an action spectrum s(λ) to emphasize wavelengths important for a particular polymer response.
- Wavelength selection: Choose a wavelength range λ1–λ2 (must be > 10 nm) relevant to the application (e.g., UV-A, UV+VIS).
- Spectral resolution: Calculations require spectral data at 1 nm resolution.
- Practical computation: Formulas are provided to compute f for both plain and action spectrum–weighted cases; Annex A gives real-world examples for commercially available solar simulators.
- Significance considerations: The standard highlights that full-spectrum simulation is unnecessary in many cases - focusing on the material-sensitive bands (UV, VIS, IR) can be more economical and technically appropriate.
Applications and Who Uses It
- Materials and plastics manufacturers: To select and validate laboratory light sources for accelerated weathering tests and to ensure reproducible degradation testing.
- Test laboratories and QA teams: For objective comparison of solar simulators (filtered xenon, fluorescent UV 340, carbon-arc, etc.) and to document conformity to reference spectra.
- R&D and material scientists: To weight spectral comparisons by action spectra of specific photochemical processes, improving relevance of accelerated testing.
- Equipment manufacturers: To design and filter solar simulators to achieve better spectral matching and to provide standardized performance metrics.
- Standards bodies and regulators: As a supporting technical report to quantify spectral matching in related test standards.
Related Standards
- ISO 4892 series (exposure to laboratory light sources)
- ISO/TR 17801 (reference global solar spectral irradiance calculated with SMARTS2)
- ASTM G177 (SMARTS2-based reference sun)
- Historical reference: CIE 85 (recalculated versions are discussed)
ISO/TR 18486:2018 helps stakeholders move from qualitative claims about spectral matching to quantitative, reproducible evaluation - improving the reliability and comparability of laboratory weathering tests.
Open preview (PDF)Plastics — Parameters comparing the spectral irradiance of a laboratory light source for weathering applications to a reference solar spectral irradiance
