Hardware Reference
In-Depth Information
Programmable applications
Programming applications are software packages which allow the user to create
software that can be used in dedicated ( turnkey ) applications and, while such
tools have something in common with a conventional language-oriented devel-
opment systems, they usually provide an environment in which applications
can be developed with minimal programming experience.
LabVIEW
National Instruments LabVIEW is a graphical application development envi-
ronment designed specifically for engineers who need to create flexible and
scalable test, measurement, and control application. LabVIEW is a fully
functional graphical programming language which offers a variety of fea-
tures that simplifies the development of sophisticated applications for control,
instrumentation, and data acquisition.
The basic building block of a LabVIEW application is a virtual instrument
(VI). This consists of a front panel which contains the user interface and an
underlying block diagram which is used to develop the visual code. Further-
more, because LabVIEW's VIs are modular, applications can be developed to
any required scale.
Figure 10.3 shows a simple LabVIEW VI which is designed to monitor and
control a process based on a heated tank. You might like to compare this with
the similar application developed in Visual Basic (see Figure 10.1).
LabVIEW's programming is based on a graphical representation of dataflow.
This model frees the developer from the usual sequential architecture of a text-
based programming language. An example of a LabVIEW VI block diagram is
shown in Figure 10.4. Components are added to this block diagram using drag
and drop techniques and then linked together. Application development is thus
extremely fast and requires very little programming expertise.
The VI shown in Figure 10.4 is designed to monitor the status of the PC's
parallel ports. The corresponding front panel view for the parallel port VI
is shown in Figure 10.5. Further examples of LabVIEW VIs are shown in
Figures 10.6-10.8.
DASYLab
DASYLab (or 'Data Acquisition Laboratory') from National Instruments pro-
vides a graphical environment for developing a range of data acquisition, display
and analysis functions (Figure 10.9). A vast range of modules permit customiza-
tion and little previous programming expertise is required to get the best from
this sophisticated yet easy to use package. However, since DASYLab is avail-
able in four different versions (Lite, Basic, Full, and Pro), it is essential to select
the version that provides the level of functionality required!
The least expensive and powerful version, DASYLab Lite, provides users
with the ability to create simple data logging applications and display the results
plotted against time. The Lite version offers only a limited number of channels
and smaller worksheets. The next level version, DASYLab Basic, can be used
to create a smart data loggers which have the ability to reduce the amount of
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