Resonant photoacoustic CO2 spectroscopy with LED light source

We have applied resonant photoacoustic sensing for carbon dioxide (CO2) detection using a mid-infrared LED light source at 4.3mm. The pressure signals are detected using a MEMS microphone. A simple cell design has been adapted to achieve an optimal enhancement of the acoustic signal. The cell can be operated both in closed and open configuration, allowing a permanent gas flow. With the components we used a compact and low-cost CO2 sensor can be realized. We present first results of our photoacoustic sensor using the binary gas mixture CO2 / nitrogen. The signals were evaluated measuring the shift in the resonance frequency of the system. The sensor shows sensitivities down to a few percent CO2. Ideas to further enhance the sensitivity of the sensor are discussed.