LabVIEW Course

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LabVIEW Course
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Week 2 Part ACreating a SubVI
You Will Learn
A. What a SubVI is B. How to create the icon and
connector C. How to use a VI as a subVI D. How to
use the Create SubVI menu option
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SubVIs
Means of using a VI in the block diagram of a
higher-level VI Requires icon and connector
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SubVI Example Calculating Slope
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Creating the Icon

• Right-click in the icon pane (Panel or Diagram)
• Always create a black and white icon

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Creating the Connector
Right-click in the icon pane (Panel only)
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Creating the Connector - cont.
Click
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The Connector Pane

• The terminal colors match the data types to which
  they are connected
• Click on the terminal to see its associated front
  panel object

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Using the VI as a SubVI

• Changes made to subVI saved in memory until saved
  to disk
• Calling subVIs
• FunctionsSelect a VI
• OR
• Drag icon onto target diagram

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Help and Classifying Terminals

• Context Help for subVIs

Classify inputs and outputs How displayed in
Context Help Window Required - Bold label
Recommended - Normal text Optional - Visible
or wire stubs shown
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Documenting the VI

• Document VIs - VI PropertiesDocumentation
• Document objects - Description and Tip...

VI Documentation
Description and Tip
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The Create SubVI Option

• Enclose area to be converted into a subVI
• Select Create SubVI from the Edit Menu

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Summary

• VIs can be used as subVIs after you make the icon
  and connector
• Icon created using Icon Editor
• Connector defined by choosing number of terminals
• Load subVIs using the Select a VI... option in
  the Functions palette or dragging the icon onto a
  new diagram
• Online help for subVIs using the Show Context
  Help option
• Descriptions document functionality
• Use Create SubVI feature to easily modularize the
  block diagram

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Week 2 Part BLoops and Charts
You Will Learn
A. About While Loops B. About waveform
charts C. How to use shift registers D. About For
Loops
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While Loop
2. Enclose code to be repeated
1. Select While Loop
3. Drop or drag additional nodes and then wire
Do (Execute diagram inside
Loop) While Condition is TRUE
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Select the Loop Condition

• Right-click on Conditional Terminal to define
  when the loop stops

Iteration Terminal
Conditional Terminal
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Waveform Charts
Selected from the ControlsGraph subpalette
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Wiring to Charts
Single-Plot Chart Multiple-Plot Chart
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Mechanical Action of Booleans

• Switch action Control is toggled until changed
  by hand
• Latch action Control reverts to default state
  when read by diagram

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Modifying Numeric Controls Indicators

• Setting the data range

• Setting the digits of precision

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Shift Registers
Available at left or right border of loop
structures Right-click on border and select Add
Shift Register Right terminal stores data on
completion of iteration Left terminal provides
stored data at beginning of next iteration
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Additional Shift Register Elements
Previous values are available at the left
terminals
Right-click on left terminal to add new elements
Right-click on the border for a new shift register
Latest value is passed to right terminal
1 loop ago 2 loops ago 3 loops ago
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Initializing Shift Registers
Initialized
Uninitialized
RUN 1
Initial Value 5
Initial Value 0
RUN 2
Initial Value 5
Initial Value 8
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Customizing Charts and Graphs

• Plot Legend (color, point style, line style,
  etc.)
• Digital Display
• Scrollbar
• Customize the
• X and Y Axes
• Graph Palette
• Scale Legend

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For Loop
In Structures subpalette of Functions
palette Enclose code to be repeated and/or
resize and add nodes inside boundary Executes
diagram inside of loop a predetermined number of
times Shift registers can be created at the
border
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Numeric Conversion

• Numeric defaults to double precision (8 bytes) or
  long integer (4 bytes)
• LabVIEW automatically converts to different
  representations
• Gray coercion dot on terminal indicates conversion

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Summary

• Two structures to repeat execution
• While Loop
• For Loop
• Loop timing controlled using Wait Until Next ms
  Multiple function
• Three modes of waveform charts
• Strip chart
• Scope chart
• Sweep chart
• Charts can be customized right-click on chart
  for menus
• Shift registers transfer data values from one
  iteration to the next
• Adapt to any data type
• Additional left terminals may be added to
  access previous
• iteration