Measuring Visual and Non-Visual Lighting Metrics in Building Environments with RGB Sensors

Abstract

Today, a spectroradiometer can measure both visual lighting metrics (illuminance, chromaticity coordinates or color temperature) and non-visual lighting metrics (Circadian Stimulus Model (CS2021) by M. Rea et al., Melanopic Equivalent Daylight (D65) Illuminance (mEDI) in CIE S 026/E: 2018) very well. Unfortunately, their cost and size make them unsuitable for practical measurements after installation. And some commercially available miniature RGB sensors can measure some visual parameters, but the question is whether they can accurately determine both visual and non-visual characteristics for practical evaluation or real-time luminaire control. Therefore, in this work, the mixed light between incident daylight and typical LED (500 lx horizontal illuminance, 4000 K) in a typical office was measured using the CSS45 spectrometer and the AS 73211 RGB sensor. Then 410/516 spectra were used to process the RGB sensor. And the remaining 20% were used to verify the obtained correlations. The correlation coefficient R2 of 0.892 and the RMSE value of 15.436 lx for the relationship between the mEDI values of the RGB sensor and the spectrophotometer and their average color difference Δu'v' of 3.78.10-5 were very good evidence for the processing. For verification, the correlation quality parameter pair (R2/RMSE) of CS2021 and Ev also reach the very good values of 0.842/0.015 and 0.78/29.15, respectively. Based on these achievements, it can be confirmed that a commercially available RGB sensor can measure the visual and non-visual parameters of lighting systems accurately enough after installation if it is properly processed as recommended in this work.

Keywords: Melanopic equivalent daylight (D65) illuminance, mEDI, Circadian Stimulus, CS2021, mEDI measurement by RGB sensors, CS2021 measurement by RGB sensors