Digital Electronics: Principles, Devices and Applications

698 Digital Electronicsthe monitor in a format as required by the user. Such an instrumentation concept is commonly referredto as virtual instrumentation.16.19.1 Use of Virtual InstrumentsThere are four types of virtual instrumentation set-up:1. A set of instruments used as a virtual instrument.2. A software graphical panel used as a virtual instrument.3. Graphical programming techniques used as a virtual instrument.4. Reconfigurable building blocks used as a virtual instrument.16.19.1.1 Set of Instruments as a Virtual InstrumentIn complex measurement situations, usually more than one instrument is required to do the intendedmeasurement. An instrumentation set-up that is used to qualify various subsystems and systems forelectromagnetic compatibility (EMC) is an example. In such a set-up, as shown in Fig. 16.38, thecomputer receives measurement data from all the stand-alone instruments, works on the data and thendisplays the measurement results. Another similar set-up that has been customized to perform a certaintest on a certain specific product, however, would not be classified as a virtual instrument.16.19.1.2 Software Graphical Panel as a Virtual InstrumentIn this type of virtual instrumentation set-up, the instrumentation hardware is controlled by a personalcomputer from a keyboard or a mouse. The PC screen is used to display the measurement results (Fig.16.39). The instrumentation hardware could be a traditional box-like instrument or a PC card offeringthe desired measurement function. The computer control of the instrument is through an interface bussuch as IEEE-488.Instrument-1Instrument-2Instrument-3ComputerFigure 16.38Set of instruments as a virtual instrument. Reproduced with permission of Fluke Corporation.