Detecting Method Of Air Negative Oxygen Ions Concentration And The System Design

Air negative oxygen ions caused a high attention in the forefront of the medical field, with the deepening of the research, air negative oxygen ion concentration’s detecting is a serious problem. The most important application of air anion concentration detector is still in atmospheric environmental monitoring. In this paper, we studied the constituent and characteristics of air anion and detection principle of air anion concentration, and designed air negative oxygen ion concentration detection system, which constituted by negative oxygen ions collector and measurement system.Firstly, we designed the negative oxygen ions collector based on ’Gerdien tube’, deduced the relationship of Gerdien tube’s main parameters, studied Computational Fluid Dynamics (CFD) technology, and applied it to the design of ions collector. Improved the internal electrode’s outline by add insulating half ellipsoid of the Gerdien tube according to underwater fluid theory, and get the dimension of improved Gerdien tube.Secondly, we analyzed the factors which affect the accuracy of air negative oxygen ions’concentration detected, proposed a method to filter other air ions by increasing inlet half ellipsoid’s short axis length. Verified the feasibility of the parameters by making numerical simulation of air negative oxygen ion concentration collector’s flow field. And made numerical simulation of collector’s electric field by ANSYS classic, then analyzed it by extracting different paths’data, which is closed to ideal value, meet the design needs. Finnaly, we summarized a set parameters of air negative oxygen ions collector.Lastly, we obtained the measurement circuit need achieved the range of lOfA-lOnA, according to the relationship of air negative oxygen ion concentration and output current. According to the principle of detecting the weak current gives a block diagram of a measurement circuit design, including Ⅰ-Ⅴ conversion, amplifier and control system module. Multi-range Ⅰ-Ⅴ conversion module was designed by Ⅰ-Ⅴ conversion module and range switch module, then by amplifying circuit amplified the output voltage of the Ⅰ-Ⅴ converter module enlarge to fit the AD conversion. We designed the each module, and analyzed the theoretical error.