Acetylene gas concentration on-line monitoring using TDLAS

A novel acetylene concentration on-line monitoring system using the tunable diode laser absorption spectroscopy(TDLAS) technology was introduced. Near infrared (NIR)distribute feedback laser diode(DFB LD) was used as light source, 0.5 m short path absorption cell, 16-bit analog-to-digital data-acquisition card obtains four channels data which should be processed by a personal computer, four channels obtain separately by varying the laser wavelength using different temperature and different light paths (signal light path and reference light path). Wavelength modulation spectroscopy(WMS) technique is slowly ramping the wavelength by scaning weak absorption lines of acetylene. Fast Fourier transform (FFT) analysis obtains the harmonic signal of absorption spectrum in the harmonic detection(HD). Because interfered by residual amplitude modulation and the laser small dc drift, some digital signal processing techniques such as mean value, digital filtering and background correction are implemented to improve the signal-to-noise ratio. Both theory analysis and experimental results show that the sensitivity of this system can meet the needs of transformer incipient fault diagnosis, which structure is compact and its calibration and adjustment of lightl path are easy.