Design Of Laser Front Drive System Applied With TDLAS Technology

In recent years,chemical industry,construction and other industries in order to cut the force of bamboo rapid development,they have brought huge economic benefits at the same time also brought a lot of pollutants,these pollutants in the atmosphere a serious threat to our physical and mental health,sealed gas chroma of indoor some gas seriously may also cause explosion dangerous behaviour,such as,so the real-time accurate testing the concentration of these gases has extremely important significance.TDLAS gas detection system has been greatly favored because of its advantages of fast response,high precision and small external influence.For the detection of methane gas,TDLAS optical theory is designed and realized the front-end driving part of TDLAS detection system.The traditional detection methods and the advantages and disadvantages of TDLAS detection method,this paper compares and analyzes the application of TDLAS detection system of the basic theory knowledge,software and hardware design part of the front drive system are introduced in detail,mainly including laser constant current source drive,laser temperature control,constant current source driving plate and temperature control board PCB production.The driving signals mainly include dc bias signal,low-frequency sawtooth scanning signal,high-frequency sinusoidal modulation signal,etc.The dc bias values corresponding to the methane gas absorption peak wavelength,the low frequency sawtooth tracing signal is used around the methane gas absorption peak in low frequency scanning,is the role of high frequency sine wave dc bias and low frequency signals for carrier,improve the anti-interference ability of the system and the signal to noise ratio.In order to avoid high frequency noise interference,LTC1064 is designed to form a fourth-order filtering system,which adopts negative feedback to adjust the stable output current,so as to realize the constant current source drive of the laser.The high precision temperature closed-loop control system for laser is designed.Because the wavelength of laser light is the dual function of drive current and temperature,in order to realize the rapid,accurate and stable control laser wavelength,first against the integral saturation of PID algorithm and neural network PID algorithm simulation test,and ultimately choose integral saturation resistance actual control PID algorithm,the experimental results show that the temperature control precision reached plus or minus 0.008 ?,implements the laser to the requirement of high precision temperature control.With experiences,the laser can emit a laser corresponding to the wavelength of 1653.72 nm of methane gas absorption peak,and can conduct low-frequency scanning around the center wavelength,and the wavelength control is accurate and stable.