LED standards published in the US

Two standards relating to LED chromaticity and photometric measurements have already been published in 2008, and more are in the pipeline.

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The ongoing controversy relating to Energy Star requirements for LED-based fixtures (see numerous articles) should not deflect from the excellent and rapid progress that has been made in developing standards for LED-based products in the US.

Back in April 2007, LEDs Magazine published an article by Kevin Dowling of Color Kinetics (now Philips), entitled "Standards required for further penetration of solid state lighting". The article described various ongoing projects to develop standards covering chromaticity, luminous flux measurement, lumen depreciation (lifetime), color quality, SSL definitions, electrical and photobiological safety, and more.

The article also included a section describing the DOE's progress towards introducing Energy Star requirements. This work will come to fruition when the DOE's criteria for Energy Star for SSL come into effect on September 30.

The DOE's Energy Star criteria draw from, and are directly related to, several of the standards that were described in Dowling's article. Of these standards, C78.377 (chromaticity) and LM-79 (luminous flux measurement) have now been published.

Chromaticity: C78.377

At the beginning of 2008, the American National Standard Lighting Group (ANSLG) published ANSI_NEMA_ANSLG C78.377-2008 entitled "Specifications for the Chromaticity of Solid State Lighting Products".

The standard can be downloaded as a PDF file for $60 from the ANSI (American National Standards Institute) website, or for free from the NEMA (National Electrical Manufacturers Association) website at www.nema.org/stds/ANSI-ANSLG-C78-377.cfm.

This standard specifies the range of chromaticities recommended for general indoor lighting with SSL products, and ensures that the white light chromaticities of the products can be communicated to consumers.

Standards
The graph at right (figure A1 in the standard) shows the chromaticity specification of SSL products, on the CIE (x,y) chromaticity diagram.

The standard applies to LED-based SSL products with control electronics and heat sinks incorporated (meaning it excludes LED chips, LED packages, and LED modules). Also, the standard covers fixtures incorporating light sources as well as integrated LED lamps, and excludes fixtures sold without a light source. (This paragraph also applies to LM-79 below.)

Photometry: LM-79

In June 2008, the Illuminating Engineering Society of North America (IESNA) published a documentary standard LM-79 entitled "Electrical and Photometric Measurements of Solid-State Lighting Products."

This describes the methods for testing SSL products for their photometric characteristics such as total luminous flux (lumens), luminous efficacy (lm/W), luminous intensity (candelas) in one or more directions, chromaticity coordinates, correlated color temperature (CCT) and color rendering index (CRI).

The most substantial part of LM-79 describes test methods for total luminous flux measurement, which is to be carried out with an integrating sphere or a goniophotometer. Crucially, LM-79 specifies absolute, rather than relative, photometry.

For other light sources and luminaires, there are separate standards for the measurement of lamps or luminaires. However, because in many current SSL products the LED light source(s) in the luminaires are not easily separable as replaceable lamps, the existing standards cannot be applied directly to SSL products.

The LM-79 document says that "since SSL technologies are still at their early stages, requirements for measurement conditions and appropriate measurement techniques may be subject to change at any time."

LM-79 can be ordered as a print version from the IESNA website. The cost is $25 to non members (30% discount to members).Click on Bookstore (upper menu bar), choose Print Publications and then in the Product ID box type in LM-79.

IESNA tells us that the company that hosts the bookstore has not yet posted it for electronic download purchase. Copies of LM-79 can also be ordered from Albert Suen in IES publication sales, email asuen@ies.org or fax 212-248-5017. Credit cards are accepted (MC, Visa, Amex).

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