Virtual Instrument Based On Sound Card And Its Applications To The Remote Electromagnetism Experiments Teaching

The virtual instrument represents an important development direction of the future instrument, and embodies the characteristic of "software is instrument". The remote experiment based on the virtual instrument, which combines virtual instrument technique with remote experiment technique, provides the students with an entirely new experiment environment.In this paper, the low-cost virtual signal generator and the virtual double-traced oscilloscope based on a PC sound card were designed, and the teaching system of the remote electromagnetism experiments based on virtual instrument technique was developed. The programs for the client computer and the experiment computer were written in virtual instrument software LabVIEW and various functions had been realized, including signal output of the virtual signal generator via the sound card, communication with the singlechip through the serial port, adjustment of the parameters of circuit elements by the singlechip, real-time acquisition of the waveform and the voltage by the virtual oscilloscope and the virtual voltage meter, Internet communication by using TCP/IP technology and so on. The port mapping between the experiment computer and the server computer was realized with IPtables Netfilter technology in Linux system, and the homepage of the teaching system of the remote electromagnetism experiments was designed with Dreamweaver and Flash, including four remote experiments, namely, "the usage of the oscilloscope ", "the transient process of RLC serial connection circuit", "the frequency characteristic of RLC serial connection circuit" and "the frequency characteristic of RLC parallel connection circuit".When students visit the website of the teaching system of the remote electromagnetism experiments, they can firstly prepare correlative contents, then conduct remote experiment by operating the emulational instrumental panel. They can adjust virtual signal generator, change parameters of circuit elements such as the resistance and the capacitance which are in the remote laboratory, acquire actual waveform and voltage, measure and analyze them with virtual oscilloscope and virtual voltage meter. So students remotely accomplish the remote electromagnetism experiments with the feelings of running actual experiments.The result of remote experiment based on virtual instrument is consistent with the result of laboratory experiment. The teaching system of the remote electromagnetism experiments based on virtual instrument technique reduces hardware requirements, and achieves a share of the experiment resource, so it is desirable that remote experiment should come into use in the experiment teaching of the college physics laboratory.