A Resonant Photoacoustic CO2 Sensor Based on MID-IR LED and MEMS Microphone Technology Operating at 4.3μm

Abstract

This paper presents work on the development of a MID-IR LED-based photoacoustic (PA) Carbon dioxide (  sensor. The transducer used is a MEMS microphone and the sensor was operated in the resonant mode, which makes it the first time that this light source and transducer combination are used in this mode for PA gas sensing, as far as the authors know. Optimisation of the sensor’s operation in the resonant mode was done using COMSOL Multiphysics to simulate the fundamental resonance frequency of the PA cell and the optimum position for the microphone. The COMSOL Multiphysics and analytical results computed were validated experimentally. Reduction of the inlet and outlet pipes diameter immensely minimized gas flow noise introduced into the PA cell. Cheaper, miniaturised and stand-alone PA sensors can be produced from Mid-IR LEDs and MEMS microphones because they are small in size, inexpensive and consume less power. The importance of this work largely lies in the fact that the huge market demand for this type of sensors could be met by higher volume production at low cost using this technology. Ultimately the work will be an effective contribution to the monitoring and control of carbon emission.

Keywords: Photoacoustic, Mid-IR LED, MEMS microphone, resonance, COMSOL