A comparison of illuminance values obtained from three illuminance measuring instruments

Abstract

In the field of occupational hygiene, light and the use of different lighting types have become fundamental control measures in reducing risks to health and safety while at the same time promoting increased productivity within the workplace. Illuminance meters are used in surveys to quantify the amount of light illuminating an object, surface, or general workplace to determine if illumination in the workplace complies with regulations and standards. Accurate illuminance measurement requires important considerations, such as the calibration conditions of illuminance meters, the spectral response of illuminance meters and the specific light source being measured. The general aim of this study was to measure and compare illuminance values obtained from the Goldilux auto-ranging light meter (GL) (MIT, South Africa), Goldilux-LED auto-ranging light meter (GL-LED) (MIT, South Africa) and the Konica Minolta CL-70f illuminance meter (KM CL- 70f) (Konica Minolta, Japan) under controlled laboratory conditions. The objectives of this study were: (i) to measure and compare the illuminance levels of halogen incandescent lamps (hICLs), compact fluorescent lamps (CFLs) and light emitting diodes (LEDs) using the GL (MIT, South Africa), the GL-LED (MIT, South Africa) and the KM CL-70f (Konica Minolta, Japan); (ii) to measure and compare the illuminance levels of low-, medium-, and high-output hICLs, CFLs and LEDs, and (iii) to measure the colour correlated temperatures (CCTs) and spectral wavelengths of each of the above-mentioned light sources with the KM CL-70f illuminance meter (Konica Minolta, Japan). The GL, GL-LED, and KM CL-70f were used to measure low-, medium-, and high-output hICLs, CFLs and LEDs precisely one metre away from the selected lamps under laboratory conditions. Background illumination in the test facility was 0 lux. Lamps were individually measured for two minutes, or until the values on the illuminance meter had stabilised. Lamp measurements were repeated three times (n=9 per lamp). Results of the GL, GL-LED, and KM CL-70f were similar when measuring low- and mediumoutput hICLs. Statistically significant differences in illuminance values were observed when measuring high-output hICLs and all CFLs and LEDs. The degree to which illuminance values differed, increased when measuring lamps with higher outputs. Spectral wavelength

measurements indicate that CFLs and LEDs have entirely different spectral qualities in comparison to the traditional ICL and hICLs. To achieve accurate measurements of modern lamps, such as CFLs and LEDs, illuminance meters having a spectral response capable of measuring the entire visible spectrum should be used. Furthermore, due to the differences in spectral wavelength qualities of lamps, illuminance meters should be calibrated to measure modern lamp types such as CFLs and LEDs. There is a need for the development of regulations and standards that define which qualities of illuminance meters are required for accurately measuring light within the workplace. Currently, there is limited information considering the minimum required quality indices such as the spectral distribution qualities or the spectral mismatch factor that illuminance meters should conform to when measuring light in the workplace. The need for development of regulations and standards, as well as the application of the GL, GL-LED and KM CL-70f in the workplace were recommended. A study limitation and future studies were also discussed.