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A highly sensitive IR-optical sensor for ethylene-monitoring

: Hartwig, S.; Hildenbrand, J.; Moreno, M.; Fonollosa, J.; Fonseca, L.; Santander, J.; Rubio, R.; Cane, C.; Lambrecht, A.; Wöllenstein, J.

Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Smart Sensors, Actuators, and MEMS II : 9-11 May 2005, Sevilla, Spain
Bellingham/Wash.: SPIE, 2005 (SPIE Proceedings Series 5836)
ISBN: 0-8194-5831-7
Conference "Microtechnologies for the New Millennium" <2005, Sevilla>
Conference Paper
Fraunhofer IPM ()
IR-spectroscopy; fruit storage; ethylene; Multiple-Reflection Cell; White cell; Fresnel lenses

Precise and continuous ethylene detection is needed in various fruit storage applications. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 µm wavelength. For this reason optical components and signal processing electronics need to be developed, tested and integrated in a compact measurement system. The present article describes the proposed system set-up, the status of the development of component prototypes and results of gas measurements performed using a first system set-up. Next to a microstructured IR-emitter, a miniaturised multi-reflection cell and a thermopile-array with integrated optical filters and microstructured Fresnel lenses for the measurement of ethylene, two interfering gases and one reference channel are proposed. Recently a miniaturised White cell as absorption path is tested with various commercial and a self-developed thermal emitter. First ethylene measurements have been performed with commercial twofold thermopile detectors and a Lock-in-amplifier. These showed significant absorption at an ethylene concentration of 100ppm. For the detection module different types of thermopiles were tested, first prototypes of Fresnel lenses have been fabricated and characterised and the parameters of the optical filters were specified. Furthermore a compact system electronics for signal processing containing a preamplification stage and Lock-in-technique is in development.