Addressing design issues when working with UVC LEDs

November 19, 2015 // By Hari Venugopalan
Hari Venugopalan, Director of Global Product Management, Crystal IS considers the design issues likely to be faced when working with UVC LEDs.

As the performance of UVC LEDs increases, adoption of this relatively new technology is gaining momentum in life sciences and environmental monitoring instrumentation. As in all emerging technologies, the designer must be aware of some fundamental differences with respect to the incumbent solution and not assume “drop-in” replacement. This allows designers to realize the full benefits of UVC LEDs. With careful consideration, UVC LEDs can decrease footprint and power consumption - improving cost of ownership for the end user.  

UVC LEDs in instrumentation  

Interest in UVC LEDs for spectroscopy is increasing as they can address market trends around miniaturization, decreasing costs, and real-time measurements. Unlike deuterium or xenon flash lamps, LEDs emit a narrow spectrum where all the light output from the device is useful for measurement. Users can select the specific peak wavelength of interest based on their application requirements. In specific applications, standardized measurement methods have been developed with a mercury lamp emission line at 254 nm. For instance, water and air quality as measured to EPA standards requires an LED closely matched to the 254 nm peak wavelength. Table 1 illustrates some of the important organic compounds in life sciences research, pharmaceutical production, and environmental monitoring that can be identified with spectroscopy.

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Table 1 Common organic compounds with peak absorption wavelength

The other primary criterion for light source selection in instrumentation is light output at the peak wavelength. Because LEDs have a single peak, the light output is concentrated at a particular wavelength, unlike other UV lamps. Absorption spectroscopy applications generally require a low level of light output – 1 mW or less. However, in cases where the flow cell is isolated from the light source, higher output is required due to significant light attenuation before the signal reaches the cell. This can raise the required light output from the LED to well over 1 mW. In fluorescence spectroscopy, signal

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