Parts-per-billion-level detection of hydrogen sulfide based on doubly resonant photoacoustic spectroscopy with line-locking

Pressure-Compensated Fiber-Optic Photoacoustic Sensors for Trace SO2 Analysis in Gas Insulation Equipment

“…The lock-in integration time is set to 1 s. Figure b shows the long-term noise of the system with a 1σ of 2.7 pm. Allan-Werle deviation analysis is used to investigate the long-term stability of the sensor. , As shown in Figure a, the detection limit is estimated to be 0.44 ppm at 1 s and can be increased to 20 ppb at 400 s. The SO 2 content in gas-insulated equipment after discharge failure is approximately tens to hundreds of ppm. The detection limit of the SO 2 sensor designed in this work for high-pressure gas-insulated equipment reaches 0.44 ppm, which can fully meet the requirements of actual engineering applications.…”

Quartz-Enhanced Photoacoustic Spectroscopy in the Terahertz Spectral Range

“…The latter was ~10 −8 cm −1 •W/ √ Hz. Currently, the NNEA~8.9 × 10 −12 cm −1 W/ √ Hz for H 2 S detection was achieved [81]. In addition, unlike sinusoidal wavelength modulation (see Equation ( 8)), in which the spectrum of the generated acoustic signal consists of the modulation frequency f mod and its weak sub-harmonics, the acoustic spectrum of a sequence of pulses with a fast rise and decay consists of many odd harmonics.…”

Ultrahigh Sensitive Trace Gas Sensing System with Dual Fiber-Optic Cantilever Multiplexing-Based Differential Photoacoustic Detection

“…Real-time monitoring of trace H 2 S concentrations is an urgent need for the safe and stable operation of the power system . The optical method , has certain advantages in H 2 S measurement. Utilizing tunable diode laser absorption spectroscopy (TDLAS) technology with an effective absorption path of 56.7 m, an H 2 S sensor with a detection limit of 224 ppb was designed .…”