Usb-based Networked Virtual Instrument System Software Development,

VI, a measurement and control system, is made up of computer hardware , modularization instrument hardware and software of data acquisition, data processing and communication. The VI is more flexible, economical and intelligent than traditional electronic measurement instrument, specially in technical feature and systematic configuration.The VI based on USB interface technology that this article develops is an application system that consists of computer and intelligent measurement module whose communication interface is based on USB. And its function is plenty, including real-time data acquisition and display, data processing, data saving and network communication. It adopts the mixed way of developping by combining VC ++, Pascal, LabWindows/CVI together. The interface of the data acquisition board based on USB and VI is achieved through transferring the DLL written by VC++. The data processing function can work on filter, windows and various kinds of spectrum analysis by FFT principle ,included magnitude spectrum, phase spectrum ,power spectrum and Harmonic frequency, etc.This article succeeds in both measurement on network and control of VI and data saving and processing based on relation Database. It can transport the acquired data to the application serve and control software for saving through network by the application serve and control software programmed by Delphi. It also can communicate concentratively with and control VI in the network of measurement and control through the application serve and control software at the same time.This article develops a powerful measurement system based on VI with a flexible configuration used by USB technology, Database technology and computer networks technology. And its application foreground is very nice. It not only fills in the VI development field based on USB, but also offers a practicable project about the network measurement system based on VI.