Virtual Instrumentation With LabVIEW

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Virtual Instrumentation With LabVIEW
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Course Goals

• Understand the components of a Virtual Instrument
• Introduce LabVIEW and common LabVIEW functions
• Build a simple data acquisition application
• Create a subroutine in LabVIEW

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Section I

• LabVIEW terms
• Components of a LabVIEW application
• LabVIEW programming tools
• Creating an application in LabVIEW

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LabVIEW Programs Are Called Virtual Instruments
(VIs)
Front Panel Controls Inputs Indicators Outputs
Block Diagram Accompanying program for front
panel Components wired together
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VI Front Panel
Panel Toolbar
Boolean Control
Double Indicator
Waveform Graph
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VI Block Diagram
Thermometer Terminal
Call to subVI
Temperature Graph
Knob Terminal
Numeric Constant
While Loop
Stop Button Terminal
Stop Loop Terminal
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Controls and Functions Palettes
Controls Palette (Panel Window)
Functions Palette (Diagram Window)
Graphical, floating palettes Used to place
controls indicators on the front panel, or to
build the block diagram
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Tools Palette

• Floating Palette
• Used to operate and modify front panel and block
  diagram objects.

• Operating Tool
• Positioning/Resizing Tool
• Labeling Tool
• Wiring Tool
• Shortcut Menu Tool

Scrolling Tool Breakpoint Tool Probe Tool Color
Copy Tool Coloring Tool

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Status Toolbar
Run Button Continuous Run Button Abort
Execution Pause/Continue Button Text
Settings Align Objects Distribute
Objects Reorder
Additional Buttons on the Diagram Toolbar
Execution Highlighting Button Step Into
Button Step Over Button Step Out Button
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Open a Virtual Instrument
Signal Generation and Processing.vi
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Creating a VI
Front Panel Window
Block Diagram Window
Indicator Terminals
Control Terminals
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Creating a VI Block Diagram
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Dataflow Programming

• Block diagram does NOT execute left to right
• Node executes when data is available to ALL input
  terminals
• Nodes supply data to all output terminals when
  done

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Exercise 1
Students build a VI that converts C to F
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Section II

• What is a subVI?
• Making an icon and connector for a subVI
• Using a VI as a subVI

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SubVIs

• A SubVI is a VI that can be used within another
  VI
• Advantages
• Modular
• Easier to debug
• Dont have to recreate code
• Require less memory

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Icon and Connector

• An icon represents a VI in other block diagrams
• A connector shows available terminals for data
  transfer

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SubVIs
SubVIs
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Steps to Create a SubVI

• Create the Icon
• Create the Connector
• Assign Terminals
• Save the VI
• Insert the VI into a Top Level VI

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Create the Icon

• Right-click on the icon in the diagram or front
  panel

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Create the Connector
Right click on the icon pane (front panel only)
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Assign Terminals
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Insert the SubVI into a Top Level VI
Accessing user-made subVIs Functions gtgt Select a
VI Or Drag icon onto target diagram
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Section III Data Acquisition

• Data acquisition (DAQ) basics
• Connecting Signals
• Simple DAQ application

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DAQ Data Acquisition

• Plug-in board for a computer with
• Analog input channels
• Analog output channels
• Counters
• Digital I/O
• Controlled by a suite of LabVIEW VIs
• FunctionsgtgtData Acquisition

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DAQ Data Acquisition

• Simple Temperature Acquisition Example
• Two parameters
• Device 1
• Channel 0

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Hardware Connections
BNC-2120
SC-2075
SCB-68
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Exercise 2

• Complete Convert C to F.vi, then create
  Thermometer.vi.

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Section IV Loops and Charts

• For Loop
• While Loop
• Charts
• Multiplots

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Loops

• While Loops
• Have Iteration Terminal
• Always Run Once
• Run According to Continue Terminal

• For Loops
• Have Iteration Terminal
• Run According to input N

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Loops (cont.)

• Select the loop
• Enclose Code to Repeat

While Loop
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Charts

• Waveform chart special numeric indicator that
  can display a history of values
• Controls gtgt Graphs gtgt Waveform Chart

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Wiring Data into Charts

• Single Plot Charts

• Multiplot Charts

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Exercise 3

• Students build Temperature Monitor.vi.

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Section V Arrays File I/O

• Build arrays manually
• Have LabVIEW build arrays automatically
• Write to a spreadsheet file
• Read from a spreadsheet file

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Adding an Array to the Front Panel

• From the Controls gtgt Array and Cluster
  subpalette, select the Array Shell

Drop it on the screen.
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Adding an Array (cont.)

• Place data object into shell (digital control,
  for example).

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Creating an Array with a Loop

• Loops accumulate arrays at their boundaries

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Creating 2D Arrays
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File I/O

• File I/O passing data to and from files
• - Files can be binary, text, or spreadsheet

Write to a spreadsheet file
Read from a spreadsheet file
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File I/O
Easy File I/O VIs

• Read/write to spreadsheet file
• Read/write characters to file (ASCII)
• Read lines from file
• Read/write binary file

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File I/O Example
Writing a 2D Array to File
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File I/O Example
Reading a 2D Array from a File
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Exercise 4
Students build Temperature Logger.vi
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Where Do I Go From Here?

• Example programs (Help Find Examples)
• LabVIEW Student Edition (www.ni.com/labviewse)
• Web resources (ni.com)
• NI Developer Zone (zone.ni.com)
• Application Notes
• Info-labview newsgroup (www.info-labview.org/)
• Instrument Driver Library (www.ni.com/idnet)