Oxygen detection system based on TDLAS–WMS and a compact multipass gas cell

Abstract

In this paper, a sensitive oxygen monitoring system was demonstrated using tunable diode laser absorption spectroscopy and wavelength modulation spectroscopy. Light from a distributed feedback laser near 760.8 nm was coupled into a compact Herriott cell with a 3.3 m optical path. A LabVIEWbased orthogonal lock-in amplifier was developed to extract the gas concentration information from the absorption signal, which can achieve baseline fitting, background deduction, filtering, and harmonic extraction. Oxygen measurement experiments were conducted, and the performance of the system was obtained. Based on an Allan deviation analysis, the minimum detection limit of the system was 0.247% at an averaging time of 1 s and could improve to 0.022% when the averaging time was 40 s.

Temperature measurement of SO2 based on mid‐infrared laser absorption spectroscopy

“…Although the K‐type thermocouple can be used to measure temperature accurately, its reliability and suitability may decrease when gas concentration is low because of the low sensitivity of the DAS. Therefore, we explored the possibility of using WMS and WMS‐2f/1f to measure temperature, which have higher sensitivity than DAS 2,14 …”

Application and algorithm research of TDLAS

“…To solve the defects of traditional methods in measuring CH4 gas concentration in pipelines, Yao Wang developed a TDLAS-based instrument for measuring CH4 concentration directly by pipeline laser [21]. Jvqiang Chang et al developed an oxygen monitoring system based on WMS-TDLAS, and the Allan variance revealed that limit of detection (LOD) of this equipment was 0.247% [22]. Weilin Ye et al introduced a CH4 measurement system based on TDLAS and LabVIEW, which used hard threshold, Coif5 wavelet basis and Heursure rule to effectively reduce the high-frequency noise of the sensor, and the minimum detection limit (MDL) of 1σ is 23.68 ppbv [23].…”

Portable TDLAS Sensor for Online Monitoring of CO2 and H2O Using a Miniaturized Multi-Pass Cell

“…Zhang et al used a commercial laser controller (CLD1015, Thorlabs), lock-in amplifier (LIA-MV-200-H, FEMTO Messtechnik GmbH, Berlin, Germany), and industrial computer (PCM-3365, Advantech Technology, China) to measure CO 2 using a TDLAS system [ 14 ]. Chang et al developed an oxygen detection system using a laptop equipped with a DAQ card (USB-6211;NI) and a LabVIEW software platform [ 28 ]. In addition, the study of miniaturized multi-pass cells (MPCs) can also improve the integration of the system [ 29 , 30 ].…”