A Remote Sensor System Based on TDLAS Technique for Ammonia Leakage Monitoring

The development of an efficient, portable, real-time, and high-precision ammonia (NH₃) remote sensor system is of great significance for environmental protection and citizens' health. We developed a NH₃ remote sensor system based on tunable diode laser absorption spectroscopy (TDLAS) technique to measure the NH₃ leakage. In order to eliminate the interference of water vapor on NH₃ detection, the wavelength-locked wavelength modulation spectroscopy technique was adopted to stabilize the output wavelength of the laser at 6612.7 cm^-1, which significantly increased the sampling frequency of the sensor system. To solve the problem in that the light intensity received by the detector keeps changing, the 2f/1f signal processing technique was adopted. The practical application results proved that the 2f/1f signal processing technique had a satisfactory suppression effect on the signal fluctuation caused by distance changing. Using Allan deviation analysis, we determined the stability and limit of detection (LoD). The system could reach a LoD of 16.6 ppm·m at an average time of 2.8 s, and a LoD of 0.5 ppm·m at an optimum averaging time of 778.4 s. Finally, the measurement result of simulated ammonia leakage verified that the ammonia remote sensor system could meet the need for ammonia leakage detection in the industrial production process.