TEMPORAL MODULATION METER TO ASSESS LIT ENVIRONMENTS

摘要

A work place receives direct emission from lamps, typically fluorescents, perhaps also from a localized incandescent one, from a natural light source if it is a diurnal journey, and all the reflexions on the ceiling, floor and walls all rounded. Still when all the fiuorescent lamps used to be connected in the same phase to the main supply, reflexions imply a change of the wave phase and an incoherent summation of waves at each point of the work place that it is somehow related with the individual contributions. There are many reports linking complains of visual pains, headaches and fatigue experimented by users of environments lighted with fluorescent systems containing magnetic ballasts (MB), with the users' performance, that seems to be affected by temporal characteristics of light. it is therefore of interest for our study to make an assessment of the real modulation of these lamps when they are activated by MB or by electronic ballasts (EB). A light modulation meter (LMM) adequate to our needs was developed. The instrument consist of a silicon photodiode sensor for the visible spectral range BPW21, whose electric signal is conditioned by means of a suitable electronic amplifier circuit, and then digitalised, processed and registered by a portable PC equipped with a digital acquisition board and a visual programming software.