Virtual Instrument For PTCR Integrated Characteristic Parameters Testing Based On DSP Technologies

Measurement of the properties of PTC materials is very important for their theoretical study and application. In this thesis, several common parameters testing theory and methods of PTCR based on PTCR testing principle and national standards are introduced. The application of virtual instrument and its development perspective, and the application of DSP (Digital Signal Processing) techniques in virtual instrument system are discussed at the beginning of this paper. Combined with these two technologies, a newly solution is proposed in parameters testing of PTCR material, and it's called PTCR parameters testing virtual instrument system based on DSP technologies. In this paper, the systematic architecture, hardware design, software design, serial communication design between PC (Personal Computer) and DSP, and some considerations on system reliability and its implementations are emphatically discussed. And the application of the system on the PTCR parameters testing is analysed by having the aging capability testing, operating time testing, recovering time testing and volt-ampere characteristic testing as examples. Undoubtedly, the virtual instrument system for PTCR characteristic parameters testing will be a very powerful tool to the parameter testing of PTC materials. With the guiding theory that software is hardware, the hardware has been simplified as it could be. The hardware of the system is consisted of several parts, such as the PC, the data collection and test controlling circuit board of DSP, the switch circuit, the protect circuit and so on. The core of the hardware is the data collection and test controlling circuit board of DSP. The real time abilities of the data collecting and control signal producing are greatly improved in virtue of the vigoroso data disposal ability and the characteristic of double-quick and accurate data operation of the DSP chip. The software of the system includes two parts, one is the DSP software and the other is PC software. The DSP program is written by using assemble language, which is very concise, takes very limited DSP resources and has a very fast calculating speed. By using Visual Studio .Net as development platform which provides a very perfect application framework and strong class libraries, and selecting C# (C Sharp) as development language which is a pure OO (Object Oriented) language in PC system, it provides high usability and extensibility of PC system. The PC system provides not only a friendly UI (User Interface) but also strong functionalities of accurate data disposing, real time graph drawing and graph printing. To minimize the development life cycle and decrease the cost of the system development, serial communication technique is adopted for data exchanging between PC and DSP. And to maximize the reliability and ability of anti-disturbing of the system, a series of software and hardware design techniques are adopted, and a special circuit is designed for protecting system from crash because of over high current.