The Design And Development And Virtual Instrument Based On Lab Windows/CVI

Testing instruments are the important tools in science research. Every instrument includes three function components. They are signal acquisition and control, signal analysis and processing, expression and output of results. The functions of traditional instruments are executed through hardware, which decides that the functions and structures of traditional instruments are only defined and manufactured by the instrument manufacturers. And the users cannot change the fuctions optionally. Though the precision, the function and the capability of traditional instruments are improved rapidly with the development of microelectronics technology and Large Scale Integrated circuit (LSI) technology, the traditional instruments are not used conveniently in situations that there are many complex testing parameters. Their localization is limited obviously. With the development of computer science technology the virtual instruments appear, which achieve the perfect combination of computer science technology and instrument technology. The three function components of instrument are executed through computer. So the functions of traditional instruments can be executed and enhanced through the computer science technology which develope rapidly. Virtual instruments initiate the new era that the instrument users can be the instrument designers. Virtual instruments delegate the direction of instruments.Conform the trend of instrument development, in this thesis the author adopts Lab Windows/CVI software development environment based on ANSI C library, using skillfully DLL technique, develops virtual signal generation, virtual display instrument respectively based on sound card and ACL-8111 data acquisition card, part of advanced arithmetic about inline signal such as small wave analysis, small wave package analysis and BP nerve network. In virtual digital displaying instrument based on sound card, the acquisition part program is finished in VC++6.0 environment using strongly function C++, mainly transfer low audio frequency functions of MMSYSTEM.DLL in Windows, adopting double deposits, achieving real-time data acquisition of sound card. Otherwisein virtual digital displaying instrument based on ACL-8111 card, the acquisition program is directly written in LabWindows/CVI with DLL technique, they both can realize real-time acquisition, real-time analysis, real-time displaying and storage function. Besides, the advanced arithmetic's about inline signal are written by based language C, they can form independent modules and can be used simply by other programs.This thesis takes LabWindows/CVI as its development environment, it can form independent setup software package and run absolutely deviating the development environment, accordingly, its setup is easy and has a strong practicability. The cantonment of parameters of the virtual instruments is all processed through the graphic interface in this thesis. The design of the interface is visual and easy to handle. Through the practical validation, compared by the traditional instruments, the testing efficiency and testing precision of the virtual instruments are much better. And the users can change, improve and expand the functions of virtual instruments through corresponding programs. They can be widely used in engineering signal analysis, fault diagnosis and so on.