Continuous monitoring of UV exposure

The German Fraunhofer institute has developed sensors capable of continuously monitoring UV intensity. UV lamps used to cure coatings and adhesives often in the food and packaging industry which require special sensors to measure the intensity of light applied.

The sensors are usually made of silicon that only deliver useful results if visible light is excluded from the measurement by external filters. Filters are very expensive and not particularly resistant to ultraviolet light so to reduce ageing, measurements can only be taken intermittently as snapshots.

Silicon carbide sensors have the advantage of being able to withstand longer exposure to UV light, but they only operate in a narrow spectral band. In the majority of industrial curing processes, it is the longer wavelengths that are of interest precisely the area in which these sensors are least accurate.

Project manager Dr. Susanne Kopta, explains: "Our sensor is based on aluminium gallium nitride technology and can withstand continuous exposure to UV light without damage. This enables it to be used for permanent inline monitoring."

A sapphire wafer serves as the substrate for the sensors with researchers cleverly applying epitaxial growth to deposit layers of the active material onto the substrate, in other words the layers have a crystalline structure.

Justin Cunningham

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