Vapor Phase Hydrogen Peroxide Sensor Based On TDLAS

In recent years,vapor phase hydrogen peroxide has been widely used in sterilization. Therefore,there is a sharp demand for effective and online measurement of the concentration of vapor-phase hydrogen peroxide.In this paper,vapor-phase hydrogen peroxide sensing system has been researched based on tunable diode laser absorption spectroscopy(TDLAS).The theoretical basis of TDLAS measuring principle is Beer-Lambert law.In Chapter 2, the physical meaning of the law is provided and the wavelength modulation technique is elaborated. The gas concentration could be inversed by the second harmonic signal.HITRAN databse is introduced in order to get the gas absorption peak.One of the detection problem based on TDLAS principle is to determine a priority target gas absorption line.Due to the absorption of hydrogen peroxide in the near-infrared band has not been updated in the HITRAN database,which increases the difficulty of the experiment.Combined with literiture research,an absorption peak was successfully found through current and temperature regulation approach.Another focus of the project is to deal with the experimental data through programming.The programming details based on Lab VIEW are specfied in this paper.Lock-in amplifier is controlled by GPIB to collect corresponding harmonic signals.Real-time second harmonic signal divided by first harmonic signal subtract the background noise,whose value of absorption peak is the ultimate relative concentration.The stability of the initial signal and the effect of humidity on experimental measurements were also studied.Finally electrochemical sensor is introduced to the calibration of TDLAS relative concentration.The TDLAS sensing system get an accuracy of 25 ppm,the detection range between 100 and 1500 ppm and the sensitivity of 1543 ppm/V.Thus,the TDLAS system is proved feasiable by experiments.