Department of Electrical Engineering and Automation

MetTLM (2021-2024)

Metrology Research Institute is involved in European Metrology Programme for Innovation and Research (EMPIR) Project MetTLM - Metrology for Temporal Light Modulation.

European union made new regulations for allowed temporal modulation in LED light sources which came to be in effect during 2021. This regulation requires the light industry and measurement instrument manufacturers to comply with a certain limit for Temporal Light Modulation (TLM) and their human eye visible part Temporal Light Artefact (TLA).

There are three different distinguished TLAs: Flicker, Stroboscopic effect, and Phantom array effect. For the first two, EU Ecodesign regulation has named metrics, PstLM and SVM for flicker and stroboscopic effect, respectively. For these, the measurement infrastructure needs to be built and validated. One of the aims of this project, that Metrology Research Institute is contributing, is to create the measurement infrastructure to measure these measurands in SI-traceable way.

Metrology Research Institute has built and validated a measurement setup [1] for PstLM and SVM measurements seen in Figure 1. This setup was used to measure a plethora of commercial LED sources to see if they are compliant with the new EU Ecodesign regulation. The lamps consisted of store-bought lamps from around 2015-2017 (EMPIR PhotoLED) and new ones bought during 2021.

The newer lamps were found out to be generally better in both measured artefacts PstLM and SVM.

Figure 1. Drawn figure of measurement setup for PstLM and SVM
Figure 1. Drawn figure of measurement setup for PstLM and SVM

Metrology Research Institute has created novel digital TLA implementations which decrease the average error when compared with the IEC recommended implementations [2]. These implementations calculate the flicker and stroboscopic effect metrics from the measured light waveforms. These implementations can be found in the Github directory [3]. We also contributed into an interlaboratory comparison within the MetTLM project for measurement of flicker and stroboscopic effect.

Contact person: Ville Mantela


1. Nordlund, Roope, Validation for Measurement of Temporal Light Artefacts on LED Light Sources, Thesis for a M. Sc. (Tech.) made in Aalto University, 2022.

2. Mantela V, Nordlund R, Askola J, Kärhä P, Ikonen E. Digital implementations for determination of temporal light artefacts of LED luminaires. Lighting Research & Technology. 2023;0(0). doi:10.1177/14771535231212404

3. Nordlund R, Mantela V. Aalto implementations for flickermeter and SVM meter [Online database]. Retrieved February 2024 from

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