LabVIEW an
Introduction
Alan Holloway
1
What is LabVIEW
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LabVIEW is a graphical programming language
that uses icons instead of lines of text to create
applications.
In contrast to text-based programming
languages, where instructions determine
program execution, LabVIEW uses dataflow
programming, where data determine execution.
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1-2
Using LabVIEW
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In LabVIEW, you build a user interface by using
a set of tools and objects.
The user interface is known as the front panel.
You then add code using graphical
representations of functions to control the front
panel objects.
The block diagram contains this code. If
organized properly, the block diagram
resembles a flowchart.
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Virtual Instruments (VI)

LabVIEW programs are called virtual
instruments, or VIs, because their appearance
and operation imitate physical instruments, such
as oscilloscopes and multimeters.
1-4
Front Panel
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The front panel is the user interface of the VI. You build
the front panel with controls and indicators, which are the
interactive input and output terminals of the VI,
respectively.
Controls are knobs, push buttons, dials, and other input
devices. Indicators are graphs, LEDs, and other
displays.
Controls simulate instrument input devices and supply
data to the block diagram of the VI. Indicators simulate
instrument output devices and display data the block
diagram acquires or generates
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LabVIEW front panel
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Block diagram
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After you build the front panel, you add code
using graphical representations of functions to
control the front panel objects.
The block diagram contains this graphical
source code.
Front panel objects appear as terminals on the
block diagram.
You cannot delete a terminal from the block
diagram. The terminal disappears only after you
delete its corresponding object on the front
panel.
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Block diagram
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Every control or indicator on
the front panel has a
corresponding terminal on
the block diagram.
Additionally, the block
diagram contains functions
and structures from built-in
LabVIEW VI libraries.
Wires connect each of the
nodes on the block diagram,
including control and
indicator terminals, functions
and structures.
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Front panel & corresponding block
diagram
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Tools palette
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The Tools palette is available on the front
panel and the block diagram.
A tool is a special operating mode of the
mouse cursor. When you select a tool, the
cursor icon changes to the tool icon.
Use the tools to operate and modify front
panel and block diagram objects.
Select View»Tools Palette from the taskbar
to display the Tools palette.
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Controls palette
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The Controls palette is only
available on the front panel.
The Controls palette contains
the front panel controls and
indicators you use to create
the user interface.
Select View» Controls Palette
or right-click the front panel
workspace to display the
Controls palette.
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Functions palette
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The Functions palette is available
only on the block diagram. The
Functions palette contains the
objects you use to program your
VI, such as arithmetic, instrument
I/O, file I/O, and data acquisition
operations.
Select View» Functions Palette
from the taskbar or right-click the
block diagram workspace to
display the Functions palette.
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Status Toolbar
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Click the Run button to run the VI. While the VI runs, the
Run button appears with a black arrow if the VI is a top-level
VI, meaning it has no callers and therefore is not a subVI.
While the VI runs, the Abort Execution button appears.
Click this button to stop the VI immediately.
Note: Avoid using the Abort Execution button to stop a VI.
Either let the VI complete its data flow or design a method to
stop the VI programmatically
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Elements of typical programs
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A - Loops
 While
loop
 For loop
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B - Decision making & file I/O
 Case
structure (if statement)
 Event structure
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C - Functions & sub VIs
 Built
in LabVIEW functions
 Creating sub VI's
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Loops
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Nearly all programs involve some sort of loop
where all or sections of the program must be
repeated.
Both the While and For Loops are located on
the Functions»Structures palette.
The For Loop differs from the While Loop in that
the For Loop executes a set number of times.
A While Loop stops executing the subdiagram
only if the value at the conditional terminal
exists.
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Drawing loops
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1 Select the
structure required
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2 Enclose the code to
be repeated (looped)
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3 Wire the appropriate
loop conditions
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Loops
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While loops
 Runs
until the stop condition is met
 Always runs at least once
 Counts number of iterations
1-17
Loops
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For loop
 Runs
according to input N number of iterations
 Counts the number of iterations
1-18
LabVIEW Functions
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What types of function are available
 Analysis
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Signal processing
Statistics
Advanced math & formulae
 Storage
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File I/O
Zip
 ARM
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specific
Simulation
Read digital I/O
 +Many
more!
1-19
Decision making
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The case structure has one or more
subdiagrams, or cases, one of which executes
when the structure executes.
The value wired to the selector terminal
determines which case to execute and can be
Boolean, string, integer or enumerated type.
Right-click the structure border to add or delete
cases. Use the Labeling tool to enter value(s) in
the case selector label and configure the
value(s) handled by each case.
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Case statement
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Boolean True/False
Numeric 0,1,2,3
…..n
String "Alan",
"Mark", "Graham"
etc
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Timing
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It may be necessary to add
some sort of timing to your
program.
You can add a timing delay
using the Wait Until Next
ms Multiple Function
Waits until the value of the
millisecond timer becomes
a multiple of the specified
millisecond multiple.
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While loop executes
every 250ms
1-22
Summary
LabVIEW programs are called virtual
instruments (VIs).
 Controls are inputs and indicators are
outputs.
 Each VI contains three main parts:
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•
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Front panel – How the user interacts with the VI
Block diagram – The code that controls the program
Icon/connector – The means of connecting a VI to
other VIs
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1-23