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MEMS analyzer for fast determination of mixed gases

: Otto, T.; Saupe, R.; Weiß, A.; Stock, V.; Throl, O.; Grählert, W.; Kaskel, S.; Schreck, H.; Gessner, T.


Dickensheets, D.L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
MOEMS and miniaturized systems VIII : 27 - 28 January 2009, San Jose, California, USA
Bellingham, WA: SPIE, 2009 (SPIE Proceedings Series 7208)
ISBN: 978-0-8194-7454-4
ISSN: 0277-786X
Paper 72080E
Conference "MOEMS and Miniaturized Systems" <8, 2009, San Jose/Calif.>
Fraunhofer ENAS ()

Quantitative determination of gas compositions are important for operation and control of different industrial processes, e.g. in thermo process line operations. Changing gas conditions are affecting such processes significantly. Thus direct measurement of these gases enables adjustment of variable gas composition very fast and precisely and can improve process and product quality. Traditional analyzers, designed primarily for laboratory use, are too large, too delicate, and too costly to deploy. Cost efficient devices can however measure individual parameters (e.g. IR absorption at a specific wavelength, heat conductivity etc.) of gases and compositions can be derived directly by calculating it online. To bridge the gap between these traditional and expensive gas analyzers and favorable, cost-effective gas measurements, we have developed a low cost MEMS-based gas analyzer system. By using near infrared spectroscopy, individual components of the mixed gas can be determined quantitatively. Also disadvantages of existing cost-effective systems like selectivity, sensitivity and measurement time is avoided. Requirements of a suitable system are precise determination and adoption of the overall optical system as well as a high wavelength stability, which represents one important condition for exact chemometric evaluation. Likewise a robust and exact spectral evaluation procedure is important. Other challenges are MEMS design and packaging as well as optimization of insensitivity against vibrations and thermal stress. In this paper, the application of MEMS analyzer in gas measuring is described and above mentioned challenges will be discussed. To demonstrate the performance of the whole system, measurement results of gas mixtures will be shown.