Metrology for Solid State Lighting

European NMI experts in photometry came together to extend their capabilities in the measurement of incandescent and fluorescent lighting to solid-state lighting (i.e. LEDs). Solid-state light sources not only generate light in an entirely different way to traditional sources but produce light with different properties, such as spectral output and angular distribution of the light produced. Therefore accurate measurements of electrical, optical and visual performance are required for the design, manufacture and quality control of solid-state lighting devices.

This EMRP project developed:

• New facilities to measure the optical parameters of solid-state lighting devices. Facilities are now available to assess the spectral and dynamic features of solid-state lighting devices. Studies were conducted of the effect of the fast-pulsed electrical inputs to solid-state devices on the colour of their output.
• New facilities to measure the key electrical parameters of solid-state lighting devices. Traceable measurement facilities are now available to measure the electrical power and power factor of solid-state lighting devices.  These measurements are essential to determine the energy efficiency of solid-state lighting devices and to assess how large-scale implementation of these sources may impact on the electrical power grid.
• Improved methods to assess luminous efficacy. This is the most important performance parameter when it comes to assessing and generating energy savings. Access to traceable measurement services is essential for manufacturers and customers for establishing confidence in product claims. The project has demonstrated that NMI facilities can reliably determine this parameter for solid-sate devices.
• Important developments towards establishing reliable life-time estimation for solid-state lighting devices. The life-time is an important economic and environmental factor in the adoption of solid-state lighting. The project developed and tested a process for accelerated aging of these long-lasting light sources.
• New facilities to measure the visual properties of solid-state lighting devices in real-world contexts. These were used to develop methods to assess key qualities of solid-state sources including colour rendition, visual comfort, and mesopic (low light) vision that are critical to consumer acceptance of solid-state lighting.

Delivering impact

Consumer confidence in the product claims for solid-state lighting is essential to increased uptake. This requires that performance assessments are based on appropriate and traceable measurement methods. This will largely be achieved via the specification of measurement methods in documentary standards. The project has made contributions to the key standards making bodies – the CIE (recognized by ISO as an international standardisation body) and CEN – including the CIE Test Standard (S-025:2015): Test Method for LED Lamps, Luminaires and LED Modules, CEN standard EN13032 published in June 2015 and a revision of EN13021 expected to be published in 2016.

Industrial uptake of improved methodologies and traceability is already underway. A manufacturer of luminance and illuminance meters participated in the project and is marketing commercial instruments for solid-state lighting that can now be made traceable to national standards at NMIs, and a calibration laboratory is aiming for accreditation in the measurement of solid-state lighting devices. Together the availability of commercial measurement instrumentation and calibration facilities increases the use of accurate measurements in the solid-state lighting supply chain. Project partners worked with Autostrade per l’Italia (that manages Italy’s highways) to investigate the use of solid-state lighting in tunnels. The work will contribute to safety critical design parameters for tunnel lighting. The project has also generated two patent applications in methods to assess LED efficiency and colour mix.  

The research outputs are being developed further in the EMRP project Metrology for efficient and safe innovative lighting. 

For more information, please contact the EURAMET Management Support Unit:
Phone: +44 20 8943 6666
E-mail: empir.msu@euramet.org