ASABE releases horticultural lighting standards for testing LEDs and SSL modules

The American Society of Agricultural and Biological Engineers (ASABE) has published the second in a series of three standards documents focused on specifying the performance of LEDs, arrays, and modules relative to the impact on plant growth and development. ASABE is an ANSI (American National Standards Institute) accredited organization and ANSI/ASABE S642 is entitled “Recommended Methods for Measurement and Testing of LED Products for Plant Growth and Development.” The standard guides LED manufacturers as to the specific methods for testing and publishing horticultural-specific specifications for LED performance and will enable SSL product developers to fairly compare products from different vendors.

The publication of S642 comes a bit more than a year after ASABE published the S640 standard that defined metrics specific to the horticultural applications. Most of the metrics that we commonly use in the SSL sector are attuned to the human visual system that has little correlation to what plants needs in terms of spectral energy.

The S642 document defines methods for testing what it calls “LED optical radiation devices” over the spectral range of 280–800 nm. As we have covered in prior articles on horticultural lighting, plants have sensitivity well beyond the human visual range and in fact beyond the PAR (photosynthetically active region) range of 400–700 nm

Manufacturers following S642 will measure the radiant or photon flux of a device under test (DUT) using metrics defined in S640. Moreover, S642 requires that the manufacturer or test lab performing the testing capture the spectral power distribution (SPD) at a minimum of 5-nm increments across the 280–800-nm range. The standard specifies the use of a goniometer system combined with a spectroradiometer and sets forth accuracy requirements for such test equipment.

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