Several types of controls and indic

Several types of controls and indicators are available. Examples of controls are knobs, push buttons, dials, and other input mechanisms. Controls simulate instru¬ment input mechanisms and supply data to the block diagram (Fig. 1.3) of the VI. Examples of indicators are graphs, LEDs, and other output displays. Indicators simulate instrument output mechanisms and display the data acquired or generated by the block diagram. Controls and indicators can handle different types of variables; it is possible to distinguish:• Numeric controls and indicators, such as slides and knobs, graphs, charts.• Boolean controls and indicators, such as buttons and switches.• String, path, array, cluster, enumerated type controls...each one associated to a certain type of data.The management of the user interface is based on the related code developed in the block diagram by using VIs and structures to get the control of the Front Panel objects. Objects in the block diagram include terminals and nodes. Block diagrams are built by connecting the objects with wires. The color and symbol of each terminal indicate the data type of the corresponding control or indicator. Constants are terminals that supply given data values to the block diagram.An example of code is reported in Fig. 1.3, which shows the block diagram associated to the Front Panel of Fig. 1.2. In this simple example, the management of the user interface is based on a While Loop. The user sets the values of the controls in the Front Panel and they are continuously acquired and sent to the VIs for signal generation. The outputs of these VIs are then combined (added) and used to compute the spectrum of the signal.LabVIEW can also be used to communicate with hardware such as data acquisi¬tion, vision, and motion control devices, as well as GPIB, PXI, VXI, RS232, and RS485 equipment. It can be both National Instruments and third party hardware. Hardware configuration is carried out through a specific interface that is illustrated in Chap. 3 in the context of the proposed application for the development of a dynamic data acquisition system based on programmable hardware.