Sdudy On The Integrated Measuring System Of Parameters For Thermistors

With very rapid innovation of new theories, development of new electronic materials and new electronic components, much higher requirements on related test technologies are demanded, but most test principles and technologies of characteristics parameter are still needed to be studied more deeply. This article focused on researching methods to test the system characteristics of thermistors, especially the four most important such as zero-power Resistance-Temperature characteristics, Current-Time characteristics, static V-I characteristics and voltage-effect. Based on the idea of system integration, put forward the systematic frame of testing thermistors system characteristics, proposed the design schemes of four main function subsystems respectively, and integrated all subsystems into one minimum universal hardware platform at very low cost (one data acquisition control unit based on PCI bus). Using this platform, called related test programs respectively to do different function test, which realized to integrate many test functions into one instrument and to be competent for testing the four system characteristics of thermistors.In this system, the electric furnace worked as the heat source, so, in order for assuring the test precision, it was a vital prerequisite to measure and control the furnace temperature precisely and reliably. By combining Fuzzy Control Theory and PI-PID control technology, this article designed one FUZZY-PI-PID compound controller, which realized automatic adaptive adjustment on PID parameters. The maximum overshoot was smaller than 2℃, and the steady state error was lower than 0.25℃. Thus, this system had the ability to intelligently control the temperature precisely.In order for improving the test system precision and assuring high reliable operation, this article described the methods of noise suppression from the designing of hardware and software respectively: removal and attenuating interference source, making the detecting circuit immune to the noise, minimizing the coupling effects in the noise transmission channel, utilizing appropriate digital filter algorithm and related detection techniques to do data processing, which finally realized very high precision system test .This test system was one multi-task real-time control system with quite complex control programs. The concepts of top-down method, modularization and hierarchical model were adopted during designing software. The final test system software was integrated by all function blocks. This article included: module of operating interface, driver module of computer and its peripheral circuit interface, temperature control module, test flow control module, pulse signal control module, switch control module, automatic shift control module, software protection alert module, drivers and control module of data acquisition card, data acquisition control module, data processing and display module, etc. This kind software design method is convenient for the management and program modification during the whole software development, which is also easy to the function expansion and upgrade.Through the practical test results obtained by this kind test system, and based on the relative thermistors materials theory, this article analyzed the four important characteristics in detail. Especially from the results of pulse voltage source, zero-power V-I characteristics, Resistance-Temperature characteristics under different voltage and Resistance-Voltage characteristics under different temperature, the thermistors voltage-effect was researched. Referring to the microstructure of thermistors, the voltage-effect mechanism was discussed. In China, it is pioneer to utilizing short pulse method to realize the automatic measurement on voltage-effect of thermistors, which is also greatly significant in much more deeply researches on its mechanism for research and development personnel.