New UV standard targets component testing for performance optimization

April 13, 2022
IES and IUVA have announced the availability of LM-92-22, a jointly developed standard outlining a measurement technique for UV-LED performance that should help drive consistency of characterization data for disinfection sources.

The Illuminating Engineering Society (IES) and International Ultraviolet Association (IUVA) recently published the first standard on the measurement of UV product emissions in a series of planned American National Standards.

ANSI/IES/IUVA LM-92-22 Approved Method: Optical and Electrical Measurement of Ultraviolet LEDs details a method for repeatable laboratory testing and measurement of UV-LED optical and electrical performance characteristics. LM-92 “covers measurement of UV LEDs in the wavelength range of 200 nm to 400 nm under continuous-pulse operation,” Alex Baker, IES manager of government affairs and public policy, told LEDs Magazine, adding that “LEDs with wavelengths longer than 360 nm are covered in ANSI/IES LM-85-20.”

Cross-industry collaboration

UV disinfection product commercialization and uptake saw a boost in response to the SARS-CoV-2 pandemic, but the development of UV standards began prior to the emergence of COVID-19. When IES and IUVA first announced their collaboration in June 2020, IUVA’s Healthcare/UV Working Group coordinator Troy Cowan stated that the group had been driving efforts toward industry consensus–based standards for UV disinfection since 2018.

The American National Standards Institute (ANSI) accredits standards developing organizations (SDOs) — such as IES — to write standards for review and approval within “a codified process,” Baker explained. “The ANSI/IES/IUVA nomenclature designates an ANSI-approved IES standard, written and published by IES, in collaboration with IUVA.”

LEDs Magazine also spoke with the National Institute of Standards and Technology (NIST) optical radiation group leader Cameron Miller, who leads the UV Working Group within the IES Testing Procedures Committee, on the importance of LM-92. Miller highlighted the need for the standard to offer a usable framework of definitions and methods that can be understood by test equipment suppliers, test and measurement technicians, and LED manufacturers alike.

NIST’s role, Miller said, is to “help U.S. industries flourish, move forward, and take away barriers. Part of that’s providing documentary standards that give everybody a level playing field.”

Miller, who leads a team of scientists that specializes in photometry and radiometry and collaborates with industry representatives to develop standardized methods for measuring optical radiation, explained that consensus standards — like LM-85, LM-80, and LM-92 — provide common methodologies and best practices for testing, evaluation, and performance that can be repeated by technicians, product developers, and third-party test services providers. “There are certain examples where [a practice] has been around so long and everybody does it,” Miller noted. “That’s accepted, but it’s not quite the common process.”

Although the IUVA is not a recognized SDO, Miller acknowledged, IES is, and the IES Testing Procedures Committee provided the right connections between IUVA members well-versed in UV-C technology, the accredited standards development process, and the parties who would be responsible for measuring and documenting UV-LED optical and electrical properties.

Missing link for UV LED measurement

“[IUVA] and [IES] had a shortlist of standards we wanted to work on to support the community,” Miller said. “This was one of [those] that needed to get out sooner than later.” He described the UV-C LED market as being in an emerging phase much like visible white-light LEDs were in the late 1990s. “There’s a lot of defect states. … There are still a lot of anomalies that the visible LED folks have eliminated by better manufacturing capabilities. With the UV LEDs, with the wider bandgap materials, it’s still a learning process in many ways. It’s rapidly advancing, but it’s still [germinating].”

Arkesso president and semiconductor industry consultant Mike Krames has expressed similar sentiments in presentations and articles featured by LEDs, although he approached the prospects by comparing visible-light and UV device architectures and applying lessons learned from blue LED advances and fabrication techniques. In 2018, Krames wrote that recent epitaxial structure developments should remove some of the limitations of photon extraction efficacy with UV LEDs, therefore increasing power-conversion efficiency and eventually making mass production less expensive.

Still, Miller explained, established measurement methods for visible LEDs, such as those documented for thermal characterization in LM-85, didn’t present entirely accurate data when applied to UV LEDs under test. That has potentially held back market expansion and commercialization of UV LEDs for disinfection applications.

“When you would apply your first pulse of electricity to some UV LEDs — actually, it’s the larger fraction — you would see the forward voltage go significantly high and then relax,” with up to a 20% shift on the measurement results, Miller explained. With LM-85, “the basis was that the forward voltage really told you what was going on with the junction temperature, and that was not the case with these UV LEDs,” he said. The junction temperature is a key indicator of how much optical radiation an LED is capable of emitting, which ultimately could make or break the real-world disinfection claims of UV-LED components and finished systems.

LEDs will not detail the test methodology here as we expect to soon publish a longer feature article on LM-92 and what LED device technology advances and challenges led to its development.

Stepping up UV standards – What’s next?

Next steps involve educating the LED product development and test/measurement sectors, Miller said, adding that “the tools [for moving ahead with this LM-92 methodology] exist, and there are companies that make perfectly acceptable products. It’s a matter of how they are used.” Further documentation on equipment calibration and characterization of detectors is forthcoming, he said.

Additionally, IES and IUVA are currently developing standards for other UV light sources, such as low-pressure mercury tubes, excimer lamps, and pulsed-xenon lamps; as well as more guidance on finished UV disinfection systems. An International Standards Organization standard, ISO 15727, for linear low-pressure mercury lamps currently exists, Miller said, but he is not aware of any other accredited standards for UV light source measurement.

ANSI/IES/IUVA LM-92-22 is available from the IES Standards library.

More on UV component/systems design and test

Disinfection demands a complete UV-C LED picture

How does UV light measurement change lighting design perspective?

UV LED sources demand calibration to precise measurements for safe operation

CARRIE MEADOWS is managing editor of LEDs Magazine, with 20+ years’ experience in business-to-business publishing across technology markets including solid-state technology manufacturing, fiberoptic communications, machine vision, lasers and photonics, and LEDs and lighting.

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About the Author

Carrie Meadows | Editor-in-Chief, LEDs Magazine

Carrie Meadows has more than 20 years of experience in the publishing and media industry. She worked with the PennWell Technology Group for more than 17 years, having been part of the editorial staff at Solid State Technology, Microlithography World, Lightwave, Portable Design, CleanRooms, Laser Focus World, and Vision Systems Design before the group was acquired by current parent company Endeavor Business Media.

Meadows has received finalist recognition for LEDs Magazine in the FOLIO Eddie Awards, and has volunteered as a judge on several B2B editorial awards committees. She received a BA in English literature from Saint Anselm College, and earned thesis honors in the college's Geisel Library. Without the patience to sit down and write a book of her own, she has gladly undertaken the role of editor for the writings of friends and family.

Meadows enjoys living in the beautiful but sometimes unpredictable four seasons of the New England region, volunteering with an animal shelter, reading (of course), and walking with friends and extended "dog family" in her spare time.