As new lighting technology moves from the laboratory, to the manufacturing line, to the retail shelf, lighting products are subjected to standards, which have been written to establish safety and performance criteria. In a way, standards help manage expectations about what the product can and cannot do and whether or not it can be safely operated for the intended applications.
Solid state lighting, in the form of lamps and fixtures that use LEDs, provides a good example of the standard-writing process. As practical LED fixtures began appearing during the years of 2000-2005, it was quickly understood that the existing standards wouldn't do - new ones would have to be written. One of those, and probably the most important, is LM-79. I call it "mysterious" because it's there, but mostly unseen by those who use LED products. However, it is the basis for rating and understanding the performance of those products and serves as a resource for a variety of certification programs.
The Standard's Objective
LM-79 was developed and is published by the Illuminating Engineering Society of North America (IES). It first appeared in 2008. The full title is: "Approved Method: Electrical and Photometric Measurements of Solid-State Lighting Products." LM-79 describes, in detail, how to accurately and reliably measure the electrical input and light output of LED products, such as integral LED bulbs and lighting fixtures. The objective of the standard is to understand how LEDs actually perform in their expected operating environment -- an enclosure or fixture with the electronics, heat sinks, optics and wiring in place. Product manufacturers are, of course, the ones most interested in such information.
Many of you may never see an LM-79 report for an LED product, but if you are a specifier, retailer or purchaser, you will see excerpts in specification sheets, product labels and catalog descriptions. Should you ask a lighting product manufacturer for a full LM-79 report of a product? Yes. It's an indicator of product quality and the basis for certification to programs such as Energy Star and listings on the California Appliance Database or the DOE's lighting product database, which is part of the DOE Compliance Certification Management System (CCMS), used by both the DOE and the Federal Trade Commission (FTC). The FTC checks the data in the DOE's lighting product database against the Lighting Facts label that appears on the product.
A Full LM-79 Report Should Include:
- Electrical Information: Input voltage, current and power (watts) along with input frequency and power factor depending upon whether the product is designed for an AC or DC supply.
- Photometric Information: Total light output (lumens), luminous efficacy expressed as lumens per watt (lm/W), luminous intensity (candelas) including a full candlepower distribution plot if appropriate for the product, chromaticity (color) coordinates, correlated color temperature (CCT) and color rendering index (CRI).
- Some reports, depending upon the laboratory, will include additional data such as a full spectral power distribution.
LM-79 reports are typically generated by a manufacturer's in-house laboratory or commercial testing laboratories that are accredited by a third-party organization - usually the National Voluntary Laboratory Accreditation Program (NVLAP).
So, while you may not want to pack a bundle of LM-79 reports into your beach bag for summer reading, I recommend becoming familiar with them if you want to compare LED (and OLED) lighting products in detail, or if you would just like to better understand the electrical and performance characteristics of this new solid state lighting technology.
