| Nowadays,in industrial waste gas detection,more and more sensor detection systems are widely used.However,most of the general detection systems use semiconductor sensors,and then these sensors are combined into an array.However,this type of sensor has a very large disadvantage that its working temperature is very high,which can reach 200 °C or even500 °C,and the energy consumption is very large,which also leads to this type of sensor.Not only the response speed is slower than other sensors,but also the sensitivity is lower.In view of the above shortcomings of semiconductor sensors : huge energy consumption,very high operating temperature and low sensitivity,a quartz crystal microbalance(QCM)sensor detection system was prepared in this paper.Firstly,the factors affecting its performance were analyzed by simulation,and then each sensor was formed into an array to develop a QCM gas detection system.Since this system absorbs gas and detects its concentration through a sensitive film on the quartz crystal surface electrode,when different sensitive film materials are coated on the electrode surface.Nondestructive testing of a variety of industrial waste gases can be achieved.The sensor has the following advantages : higher sensitivity than semiconductor sensors,and low operating temperature,can work at room temperature and low energy consumption.The work completed in this topic mainly includes the following three aspects :(1)Using the finite element analysis method,a number of QCM models based on the thickness shear vibration mode are established.This model uses AT-cut quartz wafers,and then simulates them from multiple parameter angles.Firstly,the effects of different electrode parameters,namely electrode diameter,electrode thickness,and electrode material,on the performance of single-channel QCM are analyzed.Secondly,the effects of electrode thickness and electrode spacing on the performance of multi-channel QCM sensors(dual-channel and three-channel)are analyzed.In this paper,the selected quartz crystal diameter D = 2.6mm,thickness t = 0.1mm.The simulation results show that the change of electrode parameters will lead to the change of resonant frequency of quartz crystal,thus affecting its performance.For single-channel QCM,the better electrode parameters are diameter d = 0.8mm,thickness t =0.03 mm,and the electrode material is gold.For the dual-channel QCM,the optimal electrode parameters are the spacing l = 0.5mm,the thickness t = 0.005 mm,and the electrode material is gold.For the three-channel QCM,the optimal electrode parameters are l = 0.8mm,thickness t = 0.02 mm,and the electrode material is gold.Therefore,it is very important to select the appropriate electrode parameters for the quality sensitivity of QCM.(2)Based on QCM,a gas detection system platform is built.The detection system platform should be suitable for QCM sensor array.It mainly includes the following parts :crystal oscillation circuit,power supply circuit,filter circuit,reset circuit,serial communication circuit,and host computer software.The requirement of the system is to be able to drive the circuit of the four-way QCM sensor and measure the real-time frequency.The host computer interface can detect the frequency change signal quickly and accurately,and the signal wave curve can be clearly seen.(3)Based on this sensor system,the response test of polystyrene sensitive film to toluene was carried out.The results show that the frequency is basically unchanged when the gas is not adsorbed at the beginning.As the film material gradually adsorbs the gas,the frequency gradually decreases and stabilizes.After calculation,the error accuracy of the gas concentration value is about 4 %,and the system is feasible. |
