A virtual instrument (VI) is a graphical program which consists of a program package with the features that can look and act like a real instrument.

Starting from the fact that a measuring program can be seen as a measuring instrument which is controlled by computer (PC), this means that you can replace the classic buttons, that is way it can be declared that a virtual instrument is a real tool simulated/done on the computer. Virtual instruments (VIs) can imitate the appearance and operation of real physical instruments as function generators, oscilloscopes and multimeters.

This kind of VI’s was used to develop Black Body Radiation experiment and to interconnect the sensors and emitting sources.