By: Craig DiLouie
The DOE recently published a report on the performance of new commercially available flicker meters. The study is aimed at helping lighting and meter manufacturers measure and report flicker.
Flicker—also known as “flutter” and “shimmer”—occurs in all light sources and can be roughly defined as the rapid modulation of luminous intensity. Visible flicker can be annoying, cause eyestrain and headaches, and even impair vision, making it a potential health (as well as an aesthetics) issue.
With SSL, flicker has become more important. While a welldesigned driver can minimize flicker, lower-cost products or products such as LED MR16 lamps, which have smaller control gear, may produce it.
NEMA and the Institute of Electrical and Electronics Engineers have both given attention to the issue with a position paper and recommended practice, respectively. Energy Star and California’s Title 20 are requiring reporting of flicker performance and/or consideration of adoption of flicker criteria. Manufacturers are giving it more attention and developing new products that minimize flicker.
For specifiers and distributors, the goal is to be able to evaluate products, but this requires the ability to quantitatively evaluate flicker. Manufacturers rarely report it. At issue is the fact that there is currently no standardized test procedure. (In its position paper, NEMA states that standardization is inhibited by a lack of good metrics.)
To facilitate development, the DOE studied the performance of flicker meters. Commercial meter measurements and calculations were compared against those generated by a photoelectric characterization system developed by the Pacific Northwest National Laboratory. The results show that the meters measure light intensity waveforms and calculated flicker performance similarly.
Based on the study, the DOE recommends that lighting manufacturers and testing laboratories begin testing and reporting flicker in their products. This would be based on existing metrics including Percent Flicker, Flicker Index, and Fundamental Frequency. Measurements should be taken at several points in the dimming range, as dimming can make flicker more pronounced. Ideally, as things develop, these metrics will be refined as needed or new metrics are introduced.
The DOE also suggested that specifiers may benefit by purchasing handheld meters and measuring flicker in specific products. Accurate measurement, however, requires that no light be present except from the tested source.
As flicker gets more attention, the DOE is hoping that specifiers will be more proactive in evaluating products using handheld meters, organizations will develop and refine standards as needed, and manufacturers will begin testing and reporting it. Find the report at ssl.energy.gov.
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