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Simultaneous Multiple Gas Detection Using Photoacoustic Spectroscopy


Researchers from China have developed and demonstrated a simultaneous, multi-component gas detection system based on differential Helmholtz resonance spectroscopy with a mid-infrared, tunable, interband cascade laser (ICL). The first harmonic demodulation method was used under ambient pressure to detect three light carbon gases: CH4, C2H4, and C2H6. Using this photoacoustic system, the detection limits reached 98.8 ppb, 252 ppb, and 33 ppb for methane, ethylene, and ethane, respectively. Multi-wavelength linear regression was implemented to reduce the effects of cross-interference of the three gases, maintaining the accuracy of the gas concentration measurements.

This new method, using an ICL with a Helmholtz resonator, provides a simple and fast multiple gas detection technique for atmospheric research, medicine, the food industry, pollutant monitoring, and the power industry. Researchers used Wavelength Electronics’ WTC3243 Temperature Controller to ensure ultra-stable temperature of the tunable ICL. Precise temperature control of the laser wavelength was crucial with the current ramp changing the laser wavelength only a few nanometers for the full absorption spectrum of the three gases.

With a consistent and precise laser temperature, researchers can ensure an accurate and repeatable output from the laser. They also used the WTC3293 Evaluation Board to rapidly prototype their control system. These devices enabled quick integration of the laser control system with the Helmholtz resonance spectrometer for multi-component gas detection for environmental, atmospheric, or industrial applications.

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