1. Introduction to LabVIEW
ES110

2. Graphical programming language & Data flow
LabVIEW relies on graphical symbols rather than textual language to describe programming actions
The principle of dataflow, in which functions execute only after receiving the necessary data, governs execution in a straightforward manner

3. How does LabVIEW work?
LabVIEW programs are called:
Virtual Instruments (VIs)
because their appearance and operation imitate actual instruments.
However, they are analogous to main programs, functions and subroutines from popular language like C, Fortran, Pascal, …

4. LabVIEW Programs Are Called Virtual Instruments (VIs)
Front Panel
Controls = Inputs
Indicators = Outputs
Block Diagram
Accompanying “program” for front panel
Components “wired” together
LabVIEW programs are called virtual instruments (VIs).
Stress that controls equal inputs, indicators equal outputs.
Each VI contains three main parts:
Front Panel – How the user interacts with the VI.
Block Diagram – The code that controls the program.
Icon/Connector – Means of connecting a VI to other VIs.
The Front Panel is used to interact with the user when the program is running. Users can control the program, change inputs, and see data updated in real time. Stress that controls are used for inputs- adjusting a slide control to set an alarm value, turning a switch on or off, or stopping a program. Indicators are used as outputs. Thermometers, lights, and other indicators indicate values from the program. These may include data, program states, and other information.
Every front panel control or indicator has a corresponding terminal on the block diagram. When a VI is run, values from controls flow through the block diagram, where they are used in the functions on the diagram, and the results are passed into other functions or indicators.

5. LabVIEW Introduction Two “sets” for development Wiring connections
Front Panel
Block Diagram
Wiring connections
LabVIEW Conventions
Running LabVIEW programs

6. LabVIEW Front Panel All user interface goes here!
Used to display Controls or Indicators
Highly customizable

7. LabVIEW Block Diagram Actual program Invisible to user
Read left to right, like a book
Where the MAGIC happens!

8. Terminals When you place a control (or indicator) on the FRONT PANEL
LabVIEW automatically creates a corresponding control (or indicator) terminal on the BLOCK DIAGRAM

9. Control? or Indicator?
Controls = Inputs from the user = Source Terminals
Indicators = Outputs to the user = Destinations

10. Manipulating Controls and Indicators
Right click on an indicator to
Change to control
Change format or precision
Right click on a control to
Change to indicator
Change mechanical action (whether to latch open or closed, and what to use as default…)

11. Wiring Connections Wires transport data through the block diagram
Wire color indicates variable type
A red “X” means something is wrong!

12. Wires
Wires
Node
A LabVIEW VI is held together by wires connecting nodes
and terminals; they deliver data from one source terminal to
one or more destination terminals.

13. Broken wires If you connect more than one source or no source
at all to a wire,
LabVIEW
DISAGREES with what you’re doing, and the
wire will appear broken

14. Messy vs. Clean Wiring CLEAN: Easy to troubleshoot
MESSY: What is going on?

15. Basic wires used in block diagrams and corresponding types
Each wire has different style or color, depending on the data
type that flows through the wire:
Scalar
1D array
2D array
Color
Floating-point number
orange
Integer number
blue
Boolean
green
String
pink

16. LabVIEW Conventions Front panel items Block diagram items
Controls and indicators
Block diagram items
Program structures (loops, case structures, math, etc.)
Controls vs. Indicators
Wires attach to controls on the right (give values)
Wires attach to indicators on the left (receive values)
Wiring colors
Wires are color coded to correspond to data types

17. Running LabVIEW Programs
ALMOST ALWAYS put your program in some sort of loop that can be stopped with a control
AVOID using the red “x” to stop your program

18. Lab. Equipment Oscilloscope Function Generator Digital Voltmeter (DVM)
Universal Measuring
Instruments
Signal Generator

19. Wire features together to
Tools palette . . .
Select a feature to
edit or move
Add/edit text
Operate a control
Probe Data
(troubleshoot)
Wire features together to
control flow of data

20. Insert a boolean control
Controls palette . . .
Insert a boolean control
(button or switch)
Insert a digital
indicator or control

21. Add a structure such as for, while, and case statements Add a boolean
Functions palette . . .
Add a numeric
operator (+,-,…)
Add a structure such as for,
while, and case statements
Add a boolean
operator (and, or…)
Timing/dialog
Comparison
File I/O
Signal analysis
Data Acquisition
Mathematical
Functions

22. Subpalettes . . .

23. Font ring Continuous run Distribution ring Run Stop Pause
Toolbar . . .
Font ring
Continuous run
Distribution ring
Run
Stop
Pause
Alignment ring
Debugging features
more on this later…
Reorder objects

24. The Run Button
The Run button, which looks like an arrow, starts VI execution when you click on it
It changes appearance when a VI is actually running.
When a VI won’t compile, the run button is broken

25. Examples

26. Creating a VI Front Panel Window Block Diagram Window Control
When you create an object on the Front Panel, a terminal will be created on the Block Diagram. These terminals give you access to the Front Panel objects from the Block Diagram code.
Each terminal contains useful information about the Front Panel object it corresponds to. For example, the color and symbols provide the data type. Double-precision, floating point numbers are represented with orange terminals and the letters DBL. Boolean terminals are green with TF lettering.
In general, orange terminals should wire to orange terminals, green to green, and so on. This is not a hard-and-fast rule; LabVIEW will allow a user to connect a blue terminal (integer value) to an orange terminal (fractional value), for example. But in most cases, look for a match in colors.
Controls have an arrow on the right side and have a thick border. Indicators have an arrow on the left and a thin border. Logic rules apply to wiring in LabVIEW: Each wire must have one (but only one) source (or control), and each wire may have multiple destinations (or indicators).
The program in this slide takes data from A and B and passes the values to both an Add function and a subtract function. The results are displayed on the appropriate indicators.
Control
Terminals
Indicator
Terminals

27. Example 1: Craps
From the functions – numeric panel insert a pair of dice
From the Controls panel insert a numeric digital indicator (on the front panel)
Use the wiring tool to connect the two (in the wiring diagram) and click the “run” button repeatedly.
Numbers from 0.00 to 1.00 should be displayed in the front panel

28. Example 1: Craps (continued)
Delete the wire
Add a multiplication node and a numeric constant to allow multiplication by 5
Add an addition node and numeric constant to allow addition of 1
Add a mathematical “Round to Nearest” node.
Make a second copy of this structure to represent a second die and wire them together through an addition node with an output to a numeric constant
This wiring diagram simulates the rolling
of 2 dice and their addition to form a number
from 2 through 12.

29. Example 2: Analog & Digital Voltmeter (simulated signal)
Uniform noise used as simulated signal – Functions – Signal Processing – Signal Generation menu
Absolute value function from functions – numeric menu
Mean value of data series from the functions – mathematics – Probability and Statistics menu
The 250 ms wait implemented from the time and dialog menu slows the “flutter” of the meter.

30. Example 3: Reading an analog input signal Requires A/D board to implement
From the functions menu select data acquisition and then analog input. Then select either “Sample Channel” or Sample Channels”
This places the sampling icon in your wiring diagram
You then need to configure the channel(s) and wire the output to other parts of your program.

31. Example 4: Signal Analysis (continued)

32. Example 5: Creating Sub-VIs
In wiring diagram use selection tool (mouse box) to select all items to be in the SubVI.
From Edit menu select “Create SubVI”
Double click on new icon and save it as a separate VI.
Cut-and-paste it at will or insert it using “Functions – Select VI menu”