Research Of The On-line Detection System Of Chloride Ion Based On Nano Probe Structure

Various methods have been developed for confirming the demand of chemical oxygen both in China and abroad at present,but the determination process can be disturbed by environmental factors easily.Chlorine ions,the main interfering factor,lead to an increase in oxygen demand and a slow chemical reaction by consuming a lot of oxidants and catalysts,which lead to a positive error of the measurement results.Detecting the portion of chlorine ions in the solution and getting rid of the contribution made by chlorine ions can make the final result much more closer to the practical value of the chemical oxygen demand(cod).First,the paper analyses the major influences of chloride on the determination of chemical oxygen demand(cod),expounds several common methods of the chloride ion detection,discusses the advantages and disadvantages of each method.What's more,this paper studies a kind of chloride ion detection system based on the structure of nano glass probe.Finally,the paper also gives an explanation about solution conductance measurement-feasibility of measuring ion content in the reaction solution by measuring the conductivity of the solution.Second,this paper designed an ion current detection circuit and selects the optimal design scheme through theoretical analysis.Then the circuit noise is analyzed in detail and the simulation is carried out,so the noise information of each part is obtained.What's more,the paper set up a collection part for the peripheral module,controlling part,transmission part based on FPGA controller.These modules mainly include AD module which can collect current signal data and the position data of piezoelectric ceramic,PID feedback control module for adjusting the collecting process dynamically,DA module for controling the expansion of the piezoelectric ceramics,the USB module for uploading signal data and downloading command parameters.The human-computer interaction interface is designed in LabVIEW language to store and display the data,which also can be used for setting reference value and controlling PI parameters.All functional modules can achieve the expectation in terms of practical experiment.Finally,the theory and experiments were explored and validated about the influence of the generation of ion current process,which include intensity of driving electric field,the diameter of probe tip and the concentration of electrolyte solution.the results indicate that the system has good stability and sensitivity,and has good consistency with theory.Therefore,the system can achieve rapid measurement of the concentration of chloride ions within a larger range.