Research Of Internal Resistance Of Detection Device Supercapacitors Based On AC Injection

Supercapacitors are widely used in many fields, but as the growth of the useof time, its performance will decline, if it does not carry on the real-timemonitoring, it will can cause very serious consequences. Supercapacitors have alot of important electric parameters, but most cannot accurately reflect itsperformance parameters, such as internal resistance, one of the parameters, whichcan reflect the performance changes, when supercapacitors performancedegradation or failure of its internal resistance than the rated resistance willappear obvious change in the product.Supercapacitors internal resistance is very small, about m level, so in thedesign process we need to try to overcome the influence of power frequencysignal interference on the measuring accuracy, such as; the capacity of Supercapacitor range in0.1F to1000F, so when the design must consider security.In this paper, the supercapacitors resistance detecting device is designed andbased on the principle of ac injection method, and based on the improved,making up for the deficiency of the traditional ac injection method. The detectionsystem consists of ac constant current source module, ac differential amplifiercircuit module, analog multiplier module, low-pass filtering module, A/Dconversion module and single-chip microcomputer control module of importantmodules.Application of MATLAB software establishes detection system simulationmodel, the simulation results are in line with supercapacitors rated resistancebeing measured, the correct theory shows that the detection system is right, thescheme is feasible. To join the power frequency interference signal simulation,simulation results, show that the scheme can effectively restrain power frequencyinterference.Next to the system design of the hardware of the system of some important modules of simulation and experiment was carried out, which ensures theaccuracy and stability meet the design requirements. On PC software moduledesign, program flow chart, according to the program flow chart, we completethe software programming.We should detect system for debugging and test detection systemperformance. Application test system of super capacitor were asked to test, testresults compared with the supercapacitor rated resistance, less than±1%errorrange, specification test results can be used as a super capacitor value, theinternal resistance detection system can accurately detect the supercapacitor.Finally a simple analyzed the possible causes of measurement error.