The Virtual Network Libroatory Pivotal Technology Research Based On Web

As the development of Internet and network technology, remote teaching and experiment get more and more impotent. But remote experiment, as a new way of teaching, still has some technique questions and shortage. This article has research newly and deeply on Remote Network Laboratory and brings forward an actual scheme.This article introduces on the definition, meaning and foreground of Network Virtual Laboratory, and following with the current condition and existing problem of home and abroad researching on this.Then this article introduces the class of virtual realism and network virtual laboratory. And it designs the system frame using the Internet Network technology and B/S three-layer structure.In the third part of this article, it does design to the key client technology, and does particular introductions to the login, layout and experiment process.In the forth part, it does design to the key server technology using the ASP. NET webpage program technology. ASP. NET is a webpage programming passport which characteristic is "Code-behind" . Its code is processed on the server and sends the result to the client browser. So, it can handle user's clicking-event to throw the server events to communicate with experiment equipments and operate them. And it carries out a class named "RS232" which can be used to do RS232 communication. Visual Basic.Net is a new program language which is a wholly "OOP" (Object-oriented Program) language. So that it is one of the power ASP.NET programming tools.At the last part it designs a network experiment instance: DC motor rev-control. 89C51 output the result of PID using DAC1210, 12 bit A/D convert. And the output is converted to the standard 4-20mA current output signal by V/I converter AD694. The out current signal is blown up by...