The Development Of Non-linear Conductivity Electrode And Its Measuring System

With the high speed development of society,the continuously expansion ofpopulation,the earth we live is increasingly polluted and destructed,especially thewater resource pollution problem is serious.Water quality detection has become animportant solution to monitor and manage water resource,and conductivity as the coreof water quality detection is particularly prominent.Through the conductivity valuewe can react water pollution situation,this solution have a wide range of applicationsin agriculture, industry, medicine and health care, scientific research and otherfields.How to develop both accurately and effectively,conveniently and quicklymeasure of conductivity electrode has been the scientist care about.This topic through read related literature and papers,to know the relevantelectrical conductivity measurement principle and the development of electrodecurrent situation,reference some mainstream conductivity electrode apparatus at homeand abroad,contrapose the advantage and disadvantage of these electrodes,design akind of non-linear conductivity electrode.Designing the conductance of conductivitypool structure, selecting the its material,optimizing its processing technology and theselection of electrode shape and material,base on the design process by optimizingperformance indicators, and contrast with the highest accuracy of measurement of theelectrode.The electrode design though experimental has advantage of strong workingstability, low cost, strong ability to resist pollution;it has micro pool structure,canmeasure water bodies in narrow space and eliminate the polarization phenomenoneffectively;conductivity pool has open structure,it can improve the ability of electrodeprobe to resist pollution,and reduce the frequency scaling, prolong the life of theelectrode,hope it can be able to achieve the considerable performance indicators tomatch with mainstream conductivity electrode.In terms of conductivity measuring system,by analyzing the advantages anddisadvantages of the commonly measurement methods,based on the alternatingfrequency method,i put forward a method of double frequency sinusoidal signal,thismethod can effectively eliminate the effect of capacity.Choosing the STC12C4052system as the core controller,through the MCU to control every module.Based on theworking principle of the DDFS,use ML2035chip to generate sine excitation signal,through the A/D circuit to do modulus conversion of voltage signal andelectrode output signal,converts the analog signal into MCU that can recognize thedigital signal;use RS-485communication interface to connect with computer throughserial communication way,use electromagnetic signal isolation technology on RS-485communication interface, make each part of the circuit without interference;after thecalibrating the measuring system,and test the accuracy of the measuring system.Processing the measurement data,choose MATLAB for data fitting and errorcorrection,through the fitting curve and the fitting formula for calibration.Resultsshow that the conductivity electrode I design,its temperature error is±0.89℃,therelative error of conductivity within±1%, it has good stability measurement.