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Photoacoustic CO2 sensor system - design and potential for miniaturization and integration in silicon

: Huber, Jochen; Wöllenstein, Jürgen


Sánchez-Rojas, José Luis (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems : Barcelona, Spain, 4 - 6 May 2015
Bellingham, WA: SPIE, 2015 (Proceedings of SPIE 9517)
ISBN: 978-1-62841-639-8
Paper 951715, 6 pp.
Conference "Smart Sensors, Actuators, and MEMS" <7, 2015, Barcelona>
Conference "Cyber Physical Systems" <2015, Barcelona>
Conference Paper
Fraunhofer IPM ()
carbon dioxide; CO2 sensor; miniaturization; photoacoustics; gas sensors; spectroscopy; indoor air quality

The detection of CO2 indoors has a large impact on today's sensor market. The ambient room climate is important for human health and wellbeing. The CO2 concentration is a main indicator for indoor climate and correlates with the number of persons inside a room. People in Europe spend more than 90% of their time indoors. This leads to a high demand for miniaturized and energy efficient CO2 sensors. To realize small and energy-efficient mass-market sensors, we develop novel miniaturized photoacoustic sensor systems with optimized design for real-time and selective CO2 detection. The sensor system consists of two chambers, a measurement and a detection chamber. The detection chamber consists of an integrated pressure sensor under special gas atmosphere. As pressure sensor we use a commercially available cell phone microphone. We describe a possible miniaturization process of the developed system by regarding the possibility of integration of all sensor parts. The system is manufactured in precision mechanics with IR-optical sapphire windows as optical connections. During the miniaturization process the sapphire windows are replaced by Si chips with a special IR anti-reflection coating. The developed system is characterized in detail with gas measurements and optical transmission investigations. The results of the characterization process offer a high potential for further miniaturization with high capability for mass market applications.