Optimum Design Of Heating Plate For Planar Resistance Gas Sensor

Gas Sensor has been widely used in agriculture,air monitoring,smart home,petrochemical,clinical care,transportation and other fields.Metal oxide semiconductor(MOS)gas sensors are mainly used in the civilian market of gas sensors,and its sensitive materials usually need to work at temperatures above 200oC.As a result,MOS gas sensors have a large power consumption.In this respect,it is very importance to design and optimize heating plates to reduce power consumption and improve temperature uniformity.Sensor films based on Pd-WO₃,WO₃and Sn O₂ were prepared by screen-printing technique.The structure of the heating plate was designed and with an optimization on the relative direction of electrodes and the width of sensing electrodes.Experimental results show that the maximum temperature of the heating plate with 0°relative direction is higher than that of the heating plate with 90°relative direction of the electrodes.In addition,the temperature uniformity is also improved.The high temperature region can completely cover the area where the sensing electrode located.The Pd-WO₃ sensor with 0°relative direction of the electrodes has a more sensitive response and faster response rate than that of with 90°relative direction of the electrodes.At the same time,it is verified by experiments that the heating plate has a good consistency in production process,which is suitable for mass production.The line width and spacing of the heating electrode of the A-type heating plate are also optimized.The temperature distribution and isotherm of the heating plate are simulated by the finite element simulation software COMSOL,the temperature distribution and power consumption of the heating plate are investigated by the infrared camera.The optimum line width and spacing of the heating electrodes are obtained.In order to further reduce power consumption,improve sensor response speed and improve temperature uniformity,a B-type heating plate was designed according to the laboratory conditions.Additionally,the line width and spacing of the heating electrodes were optimized,simulated and measured.Finally,the optimal line width and spacing of the heating electrodes were selected.It was proposed that a thermal insulation and electrical insulation coating film was added onto the heating electrode side of the B-type heating plate.The heating plates with different materials and thickness of coating films were simulated by the finite element simulation software COMSOL.The temperature distribution and power consumption of the heating plates were verified by the infrared camera.The results show that adding a coating film onto the top of the heating electrode can significantly reduce the power consumption of the heating plate and improve the temperature uniformity.Among them,Si O₂could be the best choice of materials,and the thinner the coating film,the better.Acetone was used as the analyte to characterize the gas sensitive response characteristics of sensors made of Pd-WO₃,WO₃ and Sn O₂.The experiment proves that the gas sensor with the coating film has better gas-sensing response performance than those without the coating film.The thinner the coating film,the faster the response rate of the sensor.The design and optimization of heating plates can improve the performance of the heating plates and gas sensors,which lays a foundation for the development of high performance MOS gas sensor.In order to develop MOS gas sensors with lower power consumption and better temperature uniformity,further research should be carried out on the new coating film materials and the encapsulation technology.