| Thermistors refer to a class of electronic components whose resistance is sensitive to temperature.According to the rate of change of resistance with temperature,they can be divided into two categories: PTCR(positive temperature coefficient thermistor)and NTCR(negative temperature coefficient thermistor).The main research content of this thesis is built around PTCR static and dynamic volt-ampere characteristics test.The volt-ampere characteristic refers to the relationship between voltage and current passed on the test sample,which together with resistance-temperature characteristic and current-time characteristic constitute the three main electrical properties of PTCR.PTC thermosensitive material is widely used in automotive parts such as diesel preheating,defrosting and low-voltage household appliances due to its unique advantages of heat resistance,pressure resistance,safe use and uniform heating.There are many PTCR manufacturers in China.Taking Haining Yongli Ceramics Co.,Ltd.as an example,the daily output is as high as 100,000 pieces.How to efficiently detect the production qualification rate and test the dynamic volt-ampere characteristics of the samples has become the main problem to be solved in this thesis.In this thesis,a design scheme of dynamic voltammetry characteristic testing system is proposed according to the uniform testing standard of the industry.The aging performance and pressure-resistant performance of PTCR were studied by combining with the matching blower,and the power attenuation rate of the sample was obtained by the experimental results.The whole test system is divided into hardware part and software part.The hardware part designs the main circuit module of the test system,and the software part realizes the development of desktop application software of the upper computer control system.The main tasks include: using serial port communication technology combined with Modbus protocol to control the load voltage required by the program-controlled power supply output test,and improving the upper limit of the original voltage output from 1000 V to 1600V;A dynamic pressurization method is designed to test the voltage shock resistance of samples.Design of overcurrent protection circuit for security module;With high reusability,good compatibility of Windows desktop application software development.At the end of this thesis,according to the experimental data obtained from the test,combined with related theories,the voltage effect and power attenuation effect of different test samples are compared and analyzed.These works have certain significance for further research in the application field of PTCR. |
