Development of a mid‐infrared early fire detection system based on dual optical path nonresonant photoacoustic cell

Abstract

A mid‐infrared carbon dioxide (CO2) sensor system was developed for early fire detection based on photoacoustic spectroscopy. A miniaturized nonresonant photoacoustic gas cell was optimized by means of finite element method (FEM). A cylindrical cell was optimized with a radius of 12.7 mm and a length of 32 mm. An approximately proportional relationship between the optical path length and the amplitude of the photoacoustic signal was observed by theoretical analysis. The optimal modulation frequency was determined to be 44 Hz. A dual optical path was adopted to gain a low limit of detection (LoD) and a high sensitivity. The amplitude of the photoacoustic signal was increased by 1.8 times compared to single optical path. The LoD of the sensor system was measured to be 4.1 ppmv at an averaging time of 84 s.

A compact portable photoacoustic sensor for sub-ppm level SO2 detection with a DUV-LED and a non-resonant photoacoustic cell

“…Therefore, a larger surface area results in greater noise generation. To address this, the photoacoustic cell structure was designed as a cylinder since cylinders have smaller surface areas compared to other volume shapes, thereby reducing noise [30]. The photoacoustic signal is produced by the absorption of a periodically modulated light beam.…”