The Testing System Of PTCR Characteristic Based On Parallel Port

Since the sixtieth year of the twentieth century, PTCR has been more and more widely used in many fields. The application of PTCR is based on the special characteristic of PTCR. So testing the parameters of PTCR is available to the extensive application of PTCR and very important.A kind of testing system of PTCR parameters is discussed in the thesis. The system adopts the idea that software is hardware. The structure of card is adopted on testing and sampling PCB. So multiplexed operation can be easily expanded and completed. The system has strong applicability and expansibility.The systematic architecture, hardware design, software design, and some considerations on Electric Magnetic Compatibility are discussed in detail in the thesis. This system used the parallel port of PC as the communication interface to control the system and receive the testing results. In view of the insufficient of the control signals offered by parallel port, latches and encoder are adopted to expand the parallel port. The application of this technology simplified the circuit structure, expanded the control bus greatly, and enhanced the applicability of the system. Some interfaces were kept for expanding system function in advance; The system adopts MAX1303 to complete analog-to-digital conversion. Meanwhile current transformer is adopted to complete high current to low current conversion as the mimic input signal of MAX1303, improve the reliability and accuracy of the system; Digital controlled power supply was realized in the system; A special circuit was designed to protect system from over current; Electric Magnetic compatibility of PCB design is discussed in the thesis to improve the stability of the system.The software system adopts C++ as program language and Visual C++ as the developing platform. Root-squaring method is adopted as AC sampling method. Twenty samples are received per cycle; The system can offer friendly operation interface; The testing of PTCR parameters is controlled by controlling program exactly; The testing results are processed and stored accurately.