Research On The Gas Concentration Detection Technology Of Quartz Crystal Photoacoustic Spectroscopy

Photoacoustic spectroscopy gas detection technology gets mature gradually.Comparing with the traditional method to detect gas concentration, the method of photoacoustic spectroscopy gas detection makes up for some shortcomings,such as the traditional detection of gas species, low precision, high maintenance cost etc and is being developed as a new detection method due to its detection effectiveness,low cost and can be used in the industrial or medical field.In this paper, the photoacoustic spectroscopy is applied to the experiment of detection gas, on this basis,designs an embedded gas concentration detection system based on ARM. Through filtering algorithm,the inspection data is used in the error processing to realize high accuracy detection of gas.At present, the measurement of the photoacoustic signal exists many problems, such as the photoacoustic signal is very weak under strong noise, so the designed photoacoustic spectroscopy system can meet the need of amplifying weak signal and picking up photoacoustic signal from strong noise. In order to design the photoacoustic spectroscopy gas detection system,this paper firstly researches the basic theory about photoacoustic spectroscopy and elaborates on the theory of photoacoustic spectroscopy gas detection.Meanwhile,it analyzes producing mechhnism, deduces basis on quartz tuning fork resonant photoacoustic signal theoretically.Then,according to photoacoustic spectroscopy,designed the related hardware and software systems.In the hardware designing,the laser from a semiconductor laser source shines photoacoustic gas pool,through quartz tuning fork produces photoacoustic signal,and processes the data using the ARM with acquisition and A/D conversion function to finish the whole design of hardware. Laser output frequency is controlled by ARM’s timer,Chopper performed by advanced timer control;The design of software includes UCOS_ii operating system design based on ARM, chopper motor control, the output of the laser frequency control, photoacoustic signal A/D conversion and correction procedures, serial port and display for the data transmission part, the design of PC VB.net application.Secondly, it uses recursive linear least squares estimation and adaptive Kalman filter for filtering photoacoustic to filter photoacoustic signal.By contrasting the filtering results, Selecting more suitable for photoacoustic signal continuity properties and higher precision adaptive Kalman filter processes the photoacoustic signal.Experimental results show that the design of optical detection of trace gas concentrations of photoacoustic spectroscopy is feasible, photoacoustic spectroscopy to detect gas concentration detection system has advantages of high precision and stability.