LabVIEWIntroduction-SixHour

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Virtual Instrumentation With LabVIEW



C ourse Goals

� Understand the components of a Virtual Instrument

� Introduce LabVIEW and common LabVIEW functions

� Build a simple data acquisition application

�C reate a subroutine in LabVIEW



S ection I

� LabVIEW terms

�C omponents of a LabVIEW application

� LabVIEW programming tools

�C reating an application in LabVIEW



Front Panel

Controls = Inputs

Indicators = Outputs

Block Diagram

Accompanying ³program´

for front panel

Components ³wired´

together

LabVIEW Programs Are C alled Virtual

Instruments (VIs)



BooleanC ontrol

DoubleIndicator

Waveform Graph

Panel Toolbar VI Front Panel



VI Block Diagram

Numeric C onstant

Thermometer Terminal C all tosubVI

While Loop

KnobTerminal

S top ButtonTerminal

S top LoopTerminal

TemperatureGraph



C ontrols and Functions Palettes

Graphical, floatingpalettes

Used to place controls &indicators on the front

panel, or to build theblock diagram

Controls Palette(Panel Window)

Functions Palette(Diagram Window)



Operating Tool

Positioning/Resizing Tool

Labeling Tool

Wiring Tool

Shortcut Menu Tool

� Floating Palette� Used to operate and modify

front panel and block diagram

objects.

Scrolling Tool

Breakpoint Tool

Probe Tool

Color Copy Tool

Coloring Tool

Tools Palette

Automatic Selection Tool



Run Button

Continuous Run Button

Abort Execution

Pause/Continue Button

Text Settings

Align Objects

Distribute Objects

Reorder

Execution HighlightingButton

Step Into Button

Step Over Button

Step Out Button

Additional Buttons on theDiagram Toolbar

S tatus Toolbar



Do Not Delete This SlideDo Not Delete This Slide



Signal Generation

and Processing.vi

Help » Find Examples«

Browse According to: Task

» Analyzing and Processing Signals

» Signal Processing

» Signal Generation and Processing.vi

O pen and Run a Virtual Instrument



ControlTerminals

Block Diagram Window

Front Panel Window

Indicator Terminals

C reating a VI



C reating a VI ± Block Diagram

�After Creating Front Panel Controls and Indicators,

Switch to Block Diagram <Ctrl-E>

�Move Front Panel Objects to Desired Locations

Using the Position/Size/Select Tool�Place Functions On Diagram

�Wire Appropriate Terminals Together to Complete

the Diagram



Wiring Tips ± Block Diagram

Wiring ³Hot Spot´

Click While Wiring To Tack Wires DownSpacebar Flips Wire Orientation

Click To Select Wires






Dataflow Programming

� Block diagram does NOT execute left to right

� Node executes when data is available to ALLinput terminals

� Nodes supply data to all output terminals whendone



H elp O ptions

Context Help� Online help

� Lock help� Simple/Complex Diagram help

� Ctrl + H

Online reference

� All menus online� Pop up on functions in diagram to access online info directly






Exercise 1 - C onvert °C to °F



Debugging Techniques

� Finding Errors

� Execution Highlighting

� Probe

Click on broken Run button

Window showing error appears

Click on Execution Highlighting button; dataflow is animated using bubbles. Values aredisplayed on wires.

Right-click on wire to display probe and itshows data as it flows through wire segment

You can also select Probe tool from Toolspalette and click on wire



S ection II ± S ubVIs

� What is a subVI?

� Making an icon and

connector for a subVI � Using a VI as a subVI



S ubVIs

�A SubVI is a VI that can be used within

another VI

�Advantages ± Modular

± Easier to debug

± Don¶t have to recreate code

± Require less memory



Icon and C onnector

� An icon represents a VI in other block diagrams

� A connector shows available terminals

for data transfer

Icon

Connector

Terminals



S ubVIs

SubVIsSubVIs



S teps to C reate a S ubVI

�C reate the Icon

�C reate the C onnector

� Assign Terminals

�S ave the VI

� Insert the VI into a Top Level VI



C reate the Icon

�Right-click on the icon in thediagram or front panel



C reate the C onnector

Right click on the icon pane (front panel only)



Assign Terminals



S ave The VI

�Choose an Easy to Remember Location

�Organize by Functionality

± Save Similar VIs into one directory (e.g. Math Utilities)

�Organize by Application ± Save all VIs Used for a Specific Application into one

directory or library file (e.g. Lab 1 ± Frequency

Response)

� Library Files (.llbs) combine many VI¶s into a single file, ideal for

transferring entire applications across computers



Insert the S ubVI into a Top Level VI

Accessing user-made subVIs

Functions >> Select a VI

Or

Drag icon onto target diagram



Tips for Working in LabVIEW

�Keystroke Shortcuts ± <Ctrl-H> ± Activate/Deactivate Context Help Window

± <Ctrl-B> ± Remove Broken Wires From Block Diagram

± <Ctrl-E> ± Toggle Between Front Panel and Block

Diagram ± <Ctrl-Z> ± Undo (Also in Edit Menu)

�Tab Key ± Toggle Through Tools on Toolbar

�Tools » Options« ± Set Preferences in LabVIEW

�VI Properties ± Configure VI Appearance,Documentation, etc.



S ection III ± Data Acquisition

�Data acquisition (DAQ) basics

�Connecting Signals

�Simple DAQ application

Computer

DAQ Device

Terminal Block

Cable

Sensors



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

Functions>>Data Acquisition



DAQ ± Data Acquisition

Simple Temperature Acquisition Example

Two parameters

�Device = 1�Channel = 0



Data Acquisition Terminology

� Resolution - Determines H ow Many Different VoltageC hanges C an Be Measured

± Larger Resolution More Precise Representation of S ignal

� Range - Minimum and Maximum Voltages ±S maller range More Precise Representation of S ignal

� Gain - Amplifies or Attenuates S ignal for Best Fit in

Range






H ardware C onnections

BNC-2120

SCB-68

SC-2075



Exercise 2 ± S imple Data Acquisition

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






S ection IV ± Loops and C harts

�For Loop

�While Loop

�Charts

�Multiplots



Loops

� While Loops ± Have Iteration Terminal

± Always Run Once

± Run According to Continue

Terminal

� For Loops

± Have Iteration Terminal

± Run According to input N



Loops (cont.)

For Loop

1. Select the loop

2. Enclose Code to

Repeat



C hartsWaveform chart ± special numeric indicator

that can display a history of values

Controls >> Graphs >> Waveform Chart



Wiring Data into C harts

Single Plot Charts Multiplot Charts



Exercise 3 ± Monitoring Temperature

Students build TemperatureMonitor.vi.



S ection V ± Arrays & File I/ O

�Build arrays manually�Have LabVIEW build arrays automatically

�Write to a spreadsheet file

�Read from a spreadsheet file



Adding an Array to the Front Panel

From the Controls >> Array and Cluster subpalette, selectthe Array Shell

Drop it on the screen.



Adding an Array (cont.)

�Place data object into shell (e.g. digitalcontrol).



C reating an Array with a Loop

� Loops accumulate arrays at their boundaries



C reating 2D Arrays



File I/ O

�Read/write to

spreadsheet file

�Read/write characters

to file (ASCII)

�Read lines from file

�Read/write binary file

Easy FileEasy File

I/O VIsI/O VIs






File I/ O Example

Writing a 2D Array to File



File I/ O Example

Reading a 2D Array from a File



Exercise 4 ± Analyzing and Logging Data

Students build TemperatureLogger.vi



S ection VI ± Array Functions & Graphs

�Basic Array Functions

�Use graphs

�Create multiplots with graphs



Array Functions ± Basics



Array Functions ± Build Array



Graphs

�Selected from the Graph palette of Controls menu

±Waveform Graph ± Plot

an array of numbers

against their indices

±XY Graph ± Plot onearray against another

±Digital Waveform Graph

± Plot bits from binary

data






Graphs

�Right-Click on the Graph to Customize



Exercise 5 ± Using Waveform Graphs



S ection VII ± S trings, C lusters, & Error H andling



S trings

� A string is a sequence of displayable or nondisplayablecharacters (ASC II)

� Many uses ± displaying messages, instrument control, file

I/ O

� S tring control/indicator is in the C ontrols»S tring subpalette



C lusters

�Data structure that groups data together

�Data may be of different types

�Analogous to struct in C

�Elements must be either all controls or all indicators

�Thought of as wires bundled into a cable





C luster Functions

� In the Cluster subpalette of the Functions palette

� Can also be accessed by right-clicking on the cluster terminal

Bundle

(Terminal labelsreflect data type)

Bundle By Name



C luster Functions

Unbundle

Unbundle By Name

Unbundled cluster in the diagram



Error C lusters

�Error cluster contains the following information: ±Boolean to report whether error occurred

±Integer to report a specific error code

±String to give information about the error



Error H andling Techniques

�Error information is passed from one subVI to thenext

� If an error occurs in one subVI, all subsequentsubVIs are not executed in the usual manner

�Error Clusters contain all error conditions

error clusters



S ection VIII - C ase & S equence S tructures,

Formula Nodes



C ase S tructures

� In the Structures subpalette of Functions palette

�Enclose nodes or drag them inside the structure

�Stacked like a deck of cards, only one case visible



Exercise 6 ± Error C lusters & H andling



S equence S tructures� In the Structures subpalette of Functions palette

�Executes diagrams sequentially, Frame 0 (0..x),where x is the total number of frames

�Stacked like a deck of cards, only one frame visible



S equence Locals�Pass data from one frame to future frames

�Created at the border of the Sequence structure

Sequence localcreated inFrame 1

Data notavailable

Dataavailable



Formula Nodes� In the Structures subpalette

� Implement complicated equations�Variables created at border

�Variable names are case sensitive

�Each statement must terminate with a semicolon (;)

�Context Help Window shows available functions

Note semicolon



S ection IX ± Printing & Documentation

� Print From File Menu to Printer, H TML, Rich Text File� Programmatically Print Graphs or Front Panel Images

� Document VIs in VI Properties » Documentation Dialog

�Add C omments Using Free Labels on Front Panel &Block Diagram



Printing

� File » Print« Gives Many Printing O ptions ±C hoose to Print Icon, Front Panel, Block Diagram, VI

H ierarchy, Included S ubVIs, VI H istory

� Print Panel.vi (Functions » Application C ontrol)Programmatically Prints a Front Panel

� Generate & Print Reports (Functions » Report

Generation)

±S earch in Find Examples for Report Generation



Documenting VIs

� VI Properties » Documentation ± Provide a Description and H elp Information for a VI

� VI Properties » Revision H istory

± Track C hanges Between Versions of a VI � Individual C ontrols » Description and Tip«

± Right C lick to Provide Description and Tip S trip

� Use Labeling Tool to Document Front Panels & Block Diagrams



S ection X ± Basic Programming Architecture

�S imple VI Architecture� General VI Architecture

�S tate Machine Architecture



S imple VI Architecture

� Functional VI that produces results when run ±No ³start´ or ³stop´ options

±S uitable for lab tests, calculations

� Example:C

onvert C

to F.vi



General VI Architecture

� Three Main S teps ±S tartup

± Main Application

±S hutdown



S tate Machine Architecture

� Advantages ± C an go from any state from any other ± Easy to modify and debug

� Disadvantages ± C an lose events if two occur at the

same time

States:

0: Startup

1: Idle

2: Event 1

3: Event 2

4: Shutdown



Exercise 7 ± S imple S tate Machine






S ection XI ± Remote Front Panels

� View & C ontrol LabVIEW Front Panels from a WebBrowser

� Requires no programming

� Remote clients see ³live´ front panel updates� Multiple clients can view the same panel

simultaneously

�Only one client can control the front panel at a time



Remote Panel Web Publishing Tool

�Tools » Web Publishing Tool«

�Click Save to Disk and

VI is Embedded into an

Html File

�After File is Saved, ItCan Be Reopened and

Customized in Any Html

Editor



Remote Front Panels - Resources

� NI Developer Zone(zone.ni.com)

± S earch for Remote Front

Panel

± Tutorials & Instructions Are Available for Download

± Information on

Incorporating Web

C ameras into RemotePanel Applications

S i XII Addi i l T i



S ection XII ± Additional Topics

� Property Nodes� Local Variables

� Global Variables

�DataS ocket

� Binary File I/ O

Wh D I G F H ?



Where Do I Go From H ere?

� Example programs ( H elp» Find Examples«)� LabVIEW S tudent 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)

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