LED based spectroscopy - A low cost solution for high resolution concentration measurements e.g. for gas monitoring applications

Reliable online sensor measurement data are the foundation of autonomous controlled processes. One important issue for a high quality production (closed loop control) as well as for environmental protection (waste reduction, reduction of harmful exhausts) is the in-situ concentration measurement of substances. Especially the selective and high resolved detection of individual substances is a complex issue for low cost sensor solutions. Optical spectroscopy is a valuable method according the selectivity and resolution but appropriate setups are quite complex (e.g. specialized light sources, spectral filtering optics, mechanical accuracy) thus they are cost intensive and almost not autonomous. This paper presents a low cost and high resolution (ppm and ppb range) spectrometric sensor system for gas detection in harsh environment. New LEDs are utilized as wavelength selective light sources in combination with standard photodiodes and optical fibers to realize robust in-situ gas measurements. Referenced measurement results for different applications are shown and discussed.