Comparison of two variants of a novel setup for real time high resolution UV-LED absorption spectroscopy

Depicted is the Development of an ultrasensitive and highly specific sensory platform. Real time, high resolution measurements of gas concentrations are a task in many applications like exhaust monitoring, smoke detectors and medical applications. Therefore were two setup approaches for UV-LED based spectroscopic gas concentration measurements investigated. By the advances in the fabrication of ultraviolet LEDs (UV-LEDs) during the past years became spectroscopic applications possible. Advantages of the UV-LED spectroscopic approach are the compact form factor, the long lifetime of the light source and small application efforts. Only a few, robust, reasonable priced components enable high volume applications. Two different hardware setups were evaluated to design the measurement system. One of the systems utilizes two concave mirrors, two photo detector diodes and a 405 nm LED mounted in a case. A standard low power microcontroller ARM Cortex M0 was applied as signal processor. The second investigated system in the comparison utilizes also the same electro optical components but applies instead of the concave mirrors polished aluminium `snail´-shaped device to increase the optical path length trough the gas. Nitrogen-dioxide (NO<sub>2</sub>) concentrations of 200 ppm are measured with a resolution of ~13% counts with the dual concave mirror setup. The aluminium `snail´ setup could not reach this sensitivity. Other gases could be measured by exchange the applied 405 nm LED with a different wave length LED.