I4.3 - Design and Simulation of a NDIR Gas Sensor System with Ray Tracing Using a Monte-Carlo Method

SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
Proceedings OPTO 2009 & IRS² 2009
IRS² 4 - Gas Analysis
J. Mayrwoeger, P. Hauer, B. Jakoby - Johannes Kepler University, Linz, Austria, W. Reichl - E+E Elektronik, Engerwitzdorf, Austria, C. Krutzler - Integrated Microsystems Austria (IMA), Wiener Neustadt, Austria
263 - 268


NDIR-gas sensors consist of basic building blocks, i.e., an IR-source, an optical path containing the sample gas, a filter, and an IR-detector. Every single part affects the behavior of the whole system. To minimize development time and costs, we investigate an efficient approach to simulate the entire sensorsystem in the beginning of the design process such that the most promising designs can be rapidly identified and pursued in the subsequent prototype engineering phase. For the analysis of optical systems, which are in the order of several thousand wavelengths, the utilization of geometrical optics rather than field-theoretic electromagnetic modeling is indicated. Specifically, we decided to use a ray tracing method applied to our specific problem.
For the results discussed below, the sample gas is CO2 corresponding to a center wavelength of the filters of 4.26 μm, the IR-sources are micro-lamps or IR-emitters, and the components for the IRdetection are bolometers or thermopiles both with integrated wavelength-dependent filters for the specified gas. The walls of the optical path are considered to be coated with a reflecting layer to act as IR mirrors. (The fabrication of the system is beyond the scope of this paper and will be discussed
The described modeling approach consists of two steps, the ray tracing computation and the postprocessing of the ray tracing results, which will be outlined in the following.