Advanced embedded control and data acquisition systems for laser-based quartz-enhanced photoacoustic spectroscopy

This work describes the development of low-power embedded systems for miniature quartz-enhanced photoacoustic spectroscopy (QEPAS) laser based trace gas sensors. Such sensors must address the following functions simultaneously: 1) laser current control, 2) laser temperature control, 3) multi-harmonic quadrature lock-in amplification, and 4) digital data processing. Currently used methods for control and acquisition result in shoebox sized sensors requiring ~3 to 4 W of electrical power consumption, which is too high for portable energy harvesting powered monitoring. In order to improve sensors to meet required size and cost demands of portable health monitors and environmental sensor networks, we have consolidated and minimized the necessary processing resources for QEPAS sensors. Our processing system has been reduced to a single 10 cm times 6.5 cm circuit board constructed entirely from low-cost off-the-shelf components, and achieves power consumption of ~0.2 W.