中文1963字Labview-based virtual function Signal GeneratorV Marozas, R Jurkonis1 IntroductionSince 1986, the U.S. NI (National Instrument) companies to the concept of virtual instrumentation, along with computer technology and measurement technology, virtual instrument technology has also been developed rapidly. Virtual instrument means: use of the existing PC, with a specially designed instrument hardware and proprietary software, the formation of the basic functions of both the ordinary instrument, there are usually no special equipment features of the new instrument. Compared with the traditional instruments of its features are: better measurement accuracy and repeatability; measurement speed; system set up time is short; instrument function defined by the user; scalability; technical updates and quick. Virtual instrument software as the core, the software company Youyi U.S. NI Labview virtual instrument software development platform most commonly used. Labview is a graphical programming language, mainly used to develop data acquisition, instrument control and data processing and analysis software, and powerful. Currently, the development of software in the international test, measurement and control industry, popular, measurement and control areas in the country has also been widely used. Function Generator is a scientific research and engineering design in a widely used general-purpose equipment. The following function signal generator with a virtual design and development of specific description is based on graphical programming language Labview virtual instrument programming and implementation of technology.2 virtual function signal generator structure and composition2.1 Virtual Function Generator front panelThis virtual function signal generator mainly consists of a PCI bus, multi-function data acquisition card and appropriate software. Them installed on a PC running Windows95/98/2000/NT the machine, shall constitute a powerful function of signal generator. The design of the virtual function signal generator reference signal generator SG 1645 power functions, front panel shown in Figure 1. Figure 1 virtual function signal generator front panelThe function generators front panel function of the following components: instrument control button, the output frequency control window (including the frequency of display units), frequency fold into control, waveform selection, frequency tuning button, dc bias, square wave accounts for Air ratio adjustment, the output waveform amplitude control buttons. Frequency tuning range: 0.1 1 Hz; DC bias: -10 10V; square wave duty cycle: 0 to 100%; output waveform range: 0 10V. Also increased the number of modification of voltage-controlled components such as panel input count input, synchronous output, voltage output. Modification of the use of these components is intended to increase the aesthetics of the instrument, and as far as possible with real instruments consistent user interface2.2 Virtual Function Signal Generator hardware structureThis virtual function signal generator hardware input and output data acquisition card and a certain configuration requirements of the PC, the data input and output depend on input data acquisition card, the definition of output achieved. This design uses the PCI-1200 data acquisition card is a good cost-effective products, with the D / A conversion functions, can generate the digital signals into analog signals and digital-analog converter and high precision, but also has filtering capabilities, which Smooth the output waveform. It supports the unipolar and bipolar analog signal input, the signal input ranges of -5 +5 V and 0 10V. Provide 16 single-ended / 8 differential analog input channels, 2 independent of the DA output channels, 24-line TTL digital I / O, 3 16-bit timer counters and other features. Some of the hardware interface for data input or output channel settings. Some of the hardware interface block diagram shown in Figure 2:Figure 23 Virtual Function Signal Generator Design and ImplementationSome use professional LabVIEW6i software virtual instrument graphical development tools. Virtual function signal generator output waveform mainly in software production and the output signal frequency display. Changes in the frequency of the output waveform is a concrete realization of data acquisition waveform data written to the buffer among the buffers by setting the update frequency (to change the internal clock frequency) to achieve the output data frequency. The process is mainly in the use of Labview data acquisition sub-module of the AO START function modules. Function from the implementation point of view, this design features a virtual function signal generator structure includes two modules: Module waveform generator (FG module) and frequency change control unit (DISPLAY) module. Waveform generator module and call FGEN module. FGEN module for the digital waveform generator