A Robust Method for Tuning Photoacoustic Gas Detectors

Detection of gases in industrial contexts is of great importance for ensuring safety in storage and transport in order to limit atmospheric pollution and precisely control industrial and agricultural processes. Although chemical sensors are in widespread use, solid-state infrared detectors for gas sensing promise numerous advantages over conventional catalytic detectors in terms of sensitivity, calibration requirements, and lifetime. The laser-modulation photoacoustic approach is an alternative. Compared to other approaches, it provides more precise measurements with a stable zero baseline, as well as having significantly less complicated optics than cavity ringdown approaches. One enduring problem, though, is the relatively long time required to make photoacoustic measurements. The key contribution of this paper to the industrial context is twofold: first, we show how a sensitive dual-buffer acoustic resonator may be fabricated using three-dimensional printing, and second, we describe a method for localizing the peak absorption more rapidly than stepping a laser through the gas absorption profile. Modeling of the proposed approach demonstrates its potential, and the expected results are confirmed using an extensive experimental setup for the detection of methane in air.