Intelligent CO2 gas microsensors and PC based signal evaluation
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Design of CO2 sensitive micro gas sensors: Transducer design, encapsulation and temperature modulated operation modes
Keyword summary: microsystem technology, temperature modulation, non-stationary state, CO2, SO2, humidity, gassensor, drift, heteropolysiloxane, polymers, single-use encapsulation, interdigital capacitor (IDC), quartz - microbalance (QMB), surface acoustic wave filter ( SAW ), artificial neuronal networks ( ANN ), fuzzy, PIC 8051, software, ANSYS, simulation, Finite Elements (FEM), VC++, Keithly Testpoint, Microsoft Windows, CAN-Bus, IEEE Bus. RS232, printer-port (EPP), DOS, Leberkässemmel, Weisswurst , Dim-Sum .
Short summary: Chemical gas sensors with sensitive layers based on polymer- or heteropolysiloxane for humidity, CO2 and SO2 have the principal advantage of a very low energy consumption and are easy downsizeable to fit into microelectronic based systems. On the downside, short- and long term drift effects as well as a rather low overall lifetime are major obstacles towards a commercial use of these sensors. Three methods were chosen to increase the system performance: Development of new transducers, a novel sensor encapsulation and the introduction of a temperature modulated mode of operation along with adapted knowledge based evaluation software. The development of o micromechanical interdigital capacitor, a directly heated quartz micro-balance and IDC-SAW combination are described. A automatically electric openable Si-based sensor encapsulation was invented. It allows a multiplication of the overall system lifetime. In the case of the micro CO2 gas sensor the application of the temperature modulated operation mode along with signal processing increases the effective sensor lifetime from less then 10 days to more than 150 days and reduces the fluctuation of the sensor sensitivity about 33%.
Please note that parts of this work are protected by German and international patents.
Click for more Information on: Patents - Publications - Awards The PhD. thesis is published in the German Engineering series "Fortschrittsberichte" (VDI Verlag Düsseldorf, Fortschrittsbericht Nr. 738, Reihe 8, ISBN 3-18-373608-X) and can be ordered through any good bookstore .
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