Design And Development Of Automated Oxygen Concentration Detector Based On Copper Ammonia Method

Oxygen is a colorless and odorless gas with combustion and oxidation properties.Oxygen has been widely used in medical,industrial,aerospace and defense industries..Oxygen concentration must meet the requirements of relevant standards especially in important application fields such as life safety,national defense science and engineering.If oxygen concentration does not meet the standards or control is not accurate,it will often lead to serious accidents.At the same time,China's plateau is vast,and the border disputes as well as the task of maintaining stability are arduous.The issue of anti-hypoxia in plateau has always been a problem restricting our army's plateau operations.Now,various types of oxygen supply equipment are widely used in the above important application fields to ensure oxygen consumption.In order to ensure the safety of oxygen use,it is necessary to measure the oxygen concentration of oxygen-making equipment regularly.In addition,the oxygen concentration should be strictly monitored during the preparation,transportation and storage of oxygen.In view of the above practical needs,it is of great practical significance to realize in-situ,rapid and accurate detection of oxygen concentration.At present,a variety of oxygen concentration detection methods have been applied at home and abroad.Although paramagnetic method,zirconia method,laser method and ion flow method are superior to the existing copper ammonia oxygen measuring device in measuring accuracy,response time and portability,these methods can not meet the actual measurement requirements for in-situ measurement of oxygen concentration under complex electromagnetic fields,low temperature and low pressure at plateau due to their vulnerability to the measurement environment.According to GB8982-2009 medical and aeronautical oxygen and GB/T3863-2008 industrial oxygen,copper-ammonia method is the standard method for oxygen concentration detection.At present,the measurement and verification institutions in China mainly use copper-ammonia method for in-situ measurement and detection of oxygen supply equipment in plateau.However,the existing copper ammonia oxygen measuring device has many shortcomings in structure,such as manual operation,subjective factors,measurement error,low efficiency,etc.It is difficult to meet the practical needs of measurement and detection.For this reason,this article,aiming at the actual demand of in-situ,fast and accurate oxygen concentration detection,especially to improve the adaptability of copper-ammonia method in Plateau and other special environments,has designed and developed an automatic oxygen concentration detection based on copper-ammonia method according to the principle of copper-ammonia method oxygen concentration detection,and on the basis of existing devices,by using electronic technology,automatic control technology and sensor technology.The prototype of the instrument has been tested and analyzed.The main contents of this research include the following parts.(1)The actual demand of oxygen concentration detection and the shortcomings and shortcomings of the existing copper-ammonia oxygen measurement device are analyzed.On this basis,the structure and function of the copper-ammonia oxygen concentration automatic detector are designed.(2)The selection of core components of the system is completed according to the system design scheme,market research and performance comparative analysis.(3)Two-dimensional engineering drawings of mechanical structure and core components of the system are completed by AutoCAD software according to the system structure design and device selection,which can guide the manufacturing and processing of the factory.(4)The prototype control system,including hardware development and software is designed and developed.(5)The prototype and debug the whole machine were assembled and the oxygen concentration in the air of a certain area in Xi'an was measured by the prototype,which had no significant difference compared with BEE-AO-210 ion flow oxygen analyzer(P > 0.05).The debugging results show that the prototype of copper ammonia oxygen concentration detector works normally and has good performance.It can complete the automatic operation of the whole process of oxygen measurement,and can carry out further performance testing experiments.(6)The performance test of the prototype is carried out in plain environment,and the uncertainty of measurement results is analyzed to verify whether the performance of the prototype meets the design requirements.The measured gases were six groups of standard gases,and each group was repeated for six times.Oxygen concentration of constant oxygen standard gases in four groups were 30.0%,49.7%,70.3%,90.0%,and that of high concentration oxygen standard gases in two groups were 99.20% and 99.60%,respectively.The experimental results show that within the evaluation range of measurement uncertainty,the six groups of standard gas measurement results contain standard values with a probability of no less than 95%.It can be concluded that the measurement results of the prototype in the plain environment are real and reliable,and the performance of the prototype meets the design requirements.(7)The performance test of the prototype is carried out In the Simulated Plateau low altitude air pressure environment,and the uncertainty of measurement results is analyzed to verify whether the performance of the prototype meets the design requirements.The explosion decompression temperature composite cabin was used to simulate the plateau environment of 3000 m,4000 m and 5000 m.The measured standard gases were 49.7% constant oxygen and 99.60% high concentration oxygen.The two groups of standard gases were measured six times in each group.The experimental results show that within the evaluation range of measurement uncertainty,the measured results of the two groups of standard gases contain standard values with a probability of no less than 95%.It can be concluded that the measured results of the prototype under the simulated plateau low altitude air pressure environment are real and reliable,and the performance of the prototype meets the design requirements.By comparing the measurements of 49.7% and 99.60% standard gases,it can be seen that there is no significant difference between the measurements of the prototype in the plain environment and the simulated plateau low altitude air pressure environment(P > 0.05),and the performance of the prototype is not affected by the low altitude air pressure environment of the plateau.Generally speaking,the prototype of copper ammonia oxygen concentration detector designed and developed in this project has the following technical characteristics.(1)The structure design of the system is reasonable.Structural design makes it easy to assemble,disassemble and maintain components.The circuit part and the vessel pipeline part realize physical isolation,no liquid cross-contamination,safe and durable.(2)The detection range is large and the measurement accuracy is high.The system can detect gases with oxygen content ranging from 0% to 100%,with repeatability ? ± 1.0%.The measurement resolution is 0.3% in the range of 0 to 99%,the indication error is ?±0.5% FS;the measurement resolution is 0.01% in the range of 99 to 100%,and the indication error is ?±3% FS.(3)The measurement error is small and the accuracy is high.The double liquid level leveling method combined with light screen sensor and stepping motor was used to replace the original manual visual leveling method,which effectively reduced the interference of human factors,reduced the system error and improved measurement accuracy.(4)The degree of automation and the efficiency of detection are improved.The bi-directional peristaltic pump is used to realize the automatic driving control of gas-liquid pipeline.The multi-gear flow rate regulation can realize the accurate collection of sample gas and the precise control of oxygen measurement process.The copper ammonia solution in the reaction bottle absorbs oxygen by turbine drive,which can effectively speed up the chemical reaction.The whole machine is operated automatically according to the predetermined measurement steps,which is convenient and fast.The single detection time is shortened from 20 minutes to less than 5 minutes.In summary,the automated oxygen concentration detector based on copper-ammonia method designed and developed in this project has achieved the expected goal.It can not only reduce the human error in the measurement process,improve the measurement accuracy and automation,but also improve the measurement efficiency and environmental adaptability,which has good practical significance and application value.