Acetylene Detection by Laser Resonant Photoacoustic Spectrometry

Acetylene always arises from the discharge faults in transformers. In order to detect it,we developed a photoacoustic spectrometer by researching the near infrared Absorption characteristic of acetylene,and analyzed the design of photoacoustic cells. By the photoacoustic spectrometer,the radiation characteristic of the distributed feedback diode laser was analyzed. The experimental results show that the radiation wavelength goes up nearly linearly with the operating temperature rising or the injecting current rising,and that the influence of the operating temperature on the radiation wavelength is higher than that of the injecting current. The photoacoustic spectrum of R(4) and R(5) in near infrared first overtone region of acetylene was gotten by taking advantage of the narrow line width and the tunability of the distributed feedback diode laser. Moreover,experimental results show that the photoacoustic signal has a significant linear correlation with the gas content and the laser power under low gas content or low laser power. The minimum detection limit of acetylene is about 1.4×10-6.