Research On Detection Technology Of The Weak Signals In The Photo Ionization Type And Infrared Spectrum Absorbed Type Gas Sensors

In the recent years,environmental pollution problems become more and more serious.So air quality measure becomes an important subject.Among many methods on the detection of the polluted gas the optical methods are issubjected gradually as its high sensitivity and high accuracy.But at present the signals coming from many optical concentration detecting systems are very weak.In addition, for the influence of the detecting system background noise, the circuit natural noise and the outside interference noise the signals which are detected will be submerged very easily.The author has researched the photo ionization technology and infrared spectrum absorbed technology respectively. Then two kinds of sensors have been designed based on this theory. And the signals obtaining from the two sensors have been detected.Firstly,the author expressed the harms which are caused by environmental pollution problems and brought up the necessities on the detection of the polluted gas concentration.Then the author listed some methods on the detection of the gas concentration and brought up the advantages of the photo ionization technology and infrared spectrum absorbed technology and their present situations home and abroad.Secondly,the author expressed the features of weak signal detecting.The features and classes and the way how to restrain them have been listed.The methods used on the weak signal detecting have been analyzed.They constitute the base of the detection on the weak signals obtaining from photo ionization sensor and infrared spectrum absorbed sensor.Finally,the author established the structure of photo ionization sensor and infrared spectrum absorbed sensor respectively.By the analysis of the signals coming from the sensors,the author obtained the features of the signals.The signal from the photo ionization sensor is pA magnitude.The signal from the infrared spectrum absorbed sensor isμV magnitude.Then the detecting circuits have been designed based on weak signal detecting principles.After that,the author did simulations and experiments.By the compare of experiment results and theoretical results,the correctness of the circuits have been validated.