Researchers from Colorado State University and Surprise, AZ have developed an ammonia sensor based on wavelength modulation spectroscopy (WMS) utilizing a quantum cascade laser (QCL) at 10.33 μm for mobile applications. The ammonia sensor was deployed on a ground vehicle for ammonia concentration measurements in a city for automobile combustion and on a fixed-wing plane for measurements in air for feedlot ammonia emissions. This compact (~20 L), lightweight (~3.5 kg), and battery-powered (<30 W) design operates autonomously to achieve a sensor accuracy of <~2% and precision of ~4 ppb in 1 s. This mobile sensing approach provides a scalable solution for detecting and quantifying anthropogenic emissions of ammonia in the atmosphere in industrial and agricultural settings.
Anthropogenic emissions contribute to greenhouse gases and gases that are significant risks to human health and the environment. Among these emissions are nitrogen (N) compounds, which add to climate change and reduce the overall ecological quality of life. A majority of nitrogen emissions from human activity come from agricultural sites. Ammonia in the air is converted from over half of the nitrogen fed to cattle in feedlots and dairies. This is directly related to the increased ammonia concentrations around feeding areas which can be over 100 times larger than typical background concentrations. Atmospheric ammonia needs to be well quantified in these areas to better regulate and reduce nitrogen anthropogenic emissions.
Laser absorption spectroscopy requires high precision and accuracy, and researchers used high-performance electronics to drive the laser system for ammonia gas detection. Laser stability is critical for sensing low concentrations of harmful gases in the air. Wavelength Electronics’ low noise laser diode driver, the FL500, can precisely deliver up to 500 mA of current and a compliance voltage of up to ~11 V to the laser, a QCL in this study. Because laser power stability or any fluctuations of the laser affect the spectra data and linewidth of the QCL, the FL500 achieves current stability at ambient temperature of 50 – 75 ppm for 24 hours, ensuring accurate and reliable results with the QCL. The FL500 also has noise as low as 3 μA RMS at full scale with a bandwidth of up to 500 kHz for current modulation or wavelength scanning. The driver enabled easy and precise wavelength scanning through the modulation of the supplied current. The small and compact design of the FL500 allows operation in mobile deployment in ground and aerial vehicles for battery powered ammonia detection using WMS with a QCL.
The complete case study is available as CS-LD11.
NEW Case Study: Laser Absorption of Atmospheric Ammonia for Mobile Measurements2025-02-132025-02-13http://teamwavelength.com/wp-content/uploads/logo_4.jpgWavelength Electronicshttps://www.teamwavelength.com/download/figure-7.png200px200px
