Study On The Key Technology And Application Of Surface Acoustic Wave Gas Sensor System

Generally,poisonous gases including poisonous gas and combustible gas.With the development of industry 4.0,it's becoming more and more reliance on petroleum and chemical industry,and some gases is produced in the petrochemical and industrial production of raw materials including the organic carbon monoxide,methane and other gases containing alkanes and volatile organic compounds(VOC)is serious harm to human life and property safety.eanwhile,as the chemical synthesis is easy to manufacture and use,which are paid attention by governments at different level to prevent all kinds of terrorist incidents,therefore,it need for toxic and harmful gases with rapid detection Gas sensor which used to detect gas component and concentration,is widely used in various kinds of gas detection and monitoring field.The test data need to be able to provide people with convenient sensor data services,so It is urgent to design the entity search service mechanism to realize multifunction,intelligence and network.These existing detection methods,such as electrochemical gas,infrared absorption method,gas chromatography and gas sensors,as complex work process,slow response,high cost and harsh environmental shortcomings limit its development.The surface acoustic wave gas sensor has the advantages of high precision,strong anti-interference ability,small volume,low power consumption,good structure and so on.It has been widely used in the field of gas detection and industrial gas detection.The characteristics of surface acoustic wave gas sensor including the sensitive mechanism of the gas,the sensitive film material and the frequency characteristic of the surface acoustic wave device.This paper based on these characteristics,designed the 3D nanowire clusters of surface acoustic wave devices,constructed the sensing signal measurement system and digital frequency processing system,and extended the research on search mechanism of sensor networks.The main research contents are:1)analyzed and compared the specific surface area difference between the structure of the two dimensional sensitive film and the structure of the three-dimensional cluster sensitive film.And based on the comprehensive consideration of selectivity,sensitivity,reversibility and performance,A kind of ZnO nanowire material was selected,and by using the liquid-phase hydrothermal method to fabricate the 3D nanowire clusters sensitive membrane.The experimental results of each ZnO nanowire clusters have 5 to 8 nanorods,with a diameter of about 150-300 nm and the length of about 3 to 4 m?.Then using the spray method to realize the synthesis of hyper branched poly of polymer and three dimensional nanowire clusters based on LSER of intermolecular force of dipole and hydrogen bond.Finally,Test results of SAW gas sensor show that the resonant frequency is 198.99 MHz,and insertion loss is-13.59 dB,which satisfies the design requirements.2)This paper used the feedback loop method to analyze and design the SAW resonance circuit of double port SAW resonator without the external signal,and also proposed a differential dual channel sensor structure.Then the detailed design process of each module in the sensor structure is introduced.Furthermore the various improved measures are proposed to improve the frequency stability and electromagnetic compatibility of the sensor.And then,proposed an improved algorithm for Rife signal detection,detection to estimate the detection circuit of the output frequency,the judgment method of Sliding Window maximize energy use,which can effectively detect the signal carrying gas sensing components.Meanwhile,designed a four sensor array structure and the back-propagation network recognition algorithm classic of poison gas sample training and recognition,so as to achieve fast and high recognition rate,recognition of single gas components,detection of low concentration and high sensitivity to poison gas concentration,and has high anti-interference ability.Through a variety of gas distribution experiment results show that a single HD toxic gas,the accurate identification rate was 100%,and the concentration error is controlled within 15%,for single sarin gas,the accurate identification rate was 100%,and the concentration error is controlled within 15%,and also for the gas mixture,the accurate identification rate was 98.79%,and in the case of the concentration lower than 1mg/m3,the concentration error is controlled within 10%,in the case of the concentration higher than 15mg/m3,the concentration error is controlled within 8%.Generally,the concentration error range is less than 15%.Then,the mixed gas added some interfering gases,such as carbon dioxide,sulfur dioxide,methane,ammonia,hydrogen sulfide,the overall of accurate identification rate was 97.37%,it shows that the sensor has high qualitative identification ability and anti disturbance ability.3)The surface acoustic wave gas sensor is composed of sensor array and pattern recognition system,which has the ability of single point gas detection and recognition.With the development of mobile Internet technology,the cloud and the end of the sensor are promoted.In this paper,based on the spatial computing ability of the gas sensor,the technology of sensor service search in ubiquitous network is studied.And analyzed the advantages and disadvantages of the existing entity search service mechanism,according to the lack of dynamic properties of the search mechanism,an accurate sensor state prediction mechanism(ASPM)was presented,which can be used to make up the deficiency of dynamic properties,and improve the search efficiency of the system.The method is to establish the historical database of physical entities,and to find the law of dynamic properties to build the model.Using the data from Intel Berkeley and NOAA laboratory show that the results of the experiment is ASPM can provide more efficient search services,while reducing the communication overhead.