Week 2 - LabVIEW Student Ambassadors_v1

8/10/2019 Week 2 - LabVIEW Student Ambassadors_v1

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TOPICS

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LabVIEW Core 1

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H. Dataflow

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Dataflow

LabVIEW follows a dataflow model for running VIs. A node executes only when data are available at all of its

required input terminals.

A node supplies data to the output terminals only when thenode finishes execution.

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Dataflow Quiz

Which node executes first?a) Addb) Subtract

c) Random Numberd) Dividee) Sine

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Dataflow Quiz Answers

No single correct answer.

Which node executes first?

a) Add Possiblyb) Subtract Definitely notc) Random Number Possiblyd) Divide Possibly

e) Sine Definitely not

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Group Exercise 1-4Concept: Dataflow

Identify dataflow execution order in the following blockdiagrams.


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Which node executes first? Last?Where are the data dependencies?


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Which Express VI executes last?


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Which Express VI executes last?


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Which Tone Measurementexecutes last?


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I. Building a Simple VI

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Building a Simple VI

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Acquire Express VIs

DAQ Assistant Express VI

Instrument I/O Assistant Express VI

Simulate Signal Express VI

Read from Measurement File Express VI

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Analyze Express VIs

Amplitude and Level Measurements Express VI

Statistics Express VI

Spectral Measurements Express VI

Tone Measurements Express VI

Filter Express VI

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Present Express VIs and Indicators

Display Message Express VI

Play Waveform Express VI

Report Express VI

Write Measurement File Express VI

DIAdem Report Express VI

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Building and Running a VI

1. Place Express VI on the block diagram.2. Configure the dialog box that opens.3. Wire Express VIs together.4. Save and run the VI.

The Run button appears broken when the VI you

are creating or editing contains errors.

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GOAL

Exercise 1-5, Part A Group ExerciseSimple Acquire, Analyze, and Present Design

Scenario: Acquire a sine waveform 0.1 seconds. Determine the average value of the waveform. Log the data. Display the data to a graph.

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DISCUSSION



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DISCUSSION


Which Express VI would you use for following tasks? Acquiring a sine wave from a data acquisition device

Determining the average value Logging data to a file Displaying data to a graph Displaying average value


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GOAL

Exercise 1-5, Part BSimple Acquire, Analyze, and Present VI

HOMEWORK

Create a simple VI that acquires data, analyzes data, andpresents the results.

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DISCUSSION

Exercise 1-5Simple Acquire, Analyze, and Present VI

How do you determine the file path of the generated text file?


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SummaryQuiz

1. Which function executes first: Add or Subtract?a) Addb) Subtractc) Unknown

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SummaryQuiz Answer

1. Which function executes first: Add or Subtract?a) Addb) Subtract

c) Unknown

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SummaryQuiz

2. Which function executes first:Sine or Divide?a) Sineb) Divide

c) Unknown

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SummaryQuiz Answer

2. Which function executes first:Sine or Divide?a) Sineb) Divide

c) Unknown

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SummaryQuiz

3. Which of the followingfunctions executes first:Random Number, Add orDivide?

a) Random Numberb) Dividec) Addd) Unknown

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SummaryQuiz Answer

3. Which of the followingfunctions executes first:Random Number, Add orDivide?

a) Random Numberb) Dividec) Addd) Unknown

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SummaryQuiz

4. Which of the followingfunctions executes last:Random Number, Subtract or Add?

a) Random Numberb) Subtractc) Addd) Unknown

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SummaryQuiz Answer

4. Which of the followingfunctions executes last:Random Number, Subtract or Add?

a) Random Numberb) Subtractc) Addd) Unknown

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SummaryQuiz Answer

5. What are the three parts of a VI?a) Front panelb) Block diagramc) Projectd) Icon/Connector pane

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TOPICS

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Lesson 2

Troubleshooting and Debugging VIs

A. Correcting Broken VIsB. Debugging TechniquesC. Undefined or Unexpected DataD. Error Handling

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A. Correcting Broken VIs

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Correcting Broken VIs

Broken Run arrow VI cannot be compiled VI cannot be executed

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Common Causes of Broken VIs

Broken wires exist on the blockdiagram. You wired a Boolean control to a

String indicator.

You wired a numeric control to anumeric control.

A required block diagramterminal is unwired.

A subVI is broken.

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B. Debugging TechniquesExecution HighlightingSingle-SteppingProbes

Breakpoints

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Debugging Techniques

What to look for if a VI produces unexpected data or behavior: Are there any unwired or hidden subVIs? Is the default data correct? Does the VI pass undefined data? Are numeric representations correct? Are node executed in the correct order?

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Execution Highlighting

Use execution highlighting to watch the data flow throughthe block diagram.

If the VI runs more slowly than expected, confirm that youturned off execution highlighting in subVIs.

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Probes

Use the Probe tool to observe intermediate datavalues and check the error output of VIsand functions, especially those performing I/O.

Specify to retain the values in the wires so that

you can probe wires for data after execution.

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Undefined or Unexpected Data

Check for unexpected Inf values or NaN values in yourmathematical operations:

(Inf) Infinity Produced by dividing a number by zero.

NaN Not a number Produced by invalid operations, such as taking the square root

of a negative number.

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GOAL

Exercise 2-1Concept: Debugging

HOMEWORK

Use the debugging tools built into LabVIEW.


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DISCUSSION

Exercise 2-1Concept: Debugging

If you have a VI with a brokenRun arrow, what should youdo first?

After you fixed your brokenRun arrow, your VI results showunexpected data. What can you do next?


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D. Error Handling Automatic and Manual Error HandlingMerge Errors FunctionError Clusters

Warnings

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Error Handling

You cannot predict every problem a user can encounter. Without a mechanism to check for errors, you know only that

the VI does not work properly. Error handling tells you why and where errors occur.

Automatic error handling Manual error handling

Error Handling Anticipation, detection,and resolution of warnings and errors

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Automatic Error Handling

By default, LabVIEW automatically handles any known errorwhen a VI runs by: Suspending execution. Highlighting the subVI or function where the error occurred. Displaying theError list window.

Automatic error handling is: Acceptable for quick prototypes.

Not recommended for professional application development. Not included in LabVIEW-built executables.

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DEMONSTRATION

Automatic vs. Manual Error Handling

Demonstrate the difference between automatic and manualerror handling.


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Disable Automatic Error Handling

Options Dialog Box Block Diagram page Uncheck

Enable automatic error handling in new VIs Enable automatic error handling dialogs

Other suggested changes Front Panel page

Set Control Style for New VIs toSilver style Block Diagram page

Uncheck Place front panel terminals as icons

ConfigureBlock Diagram Cleanup to customize your block diagram

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Merge Errors

Propagate errors along wires. Merge errors from different wire paths.

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Merge Errors Function

Merge Errors function returns the first error found. If no erroris found, it returns the first warning. The Merge Errors function does not concatenate errors.

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Error Clusters

Use the error cluster controls and indicators to create errorinputs and outputs in subVIs. The error in and error

out clusters include thefollowing componentsof information: Status

Code Source

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Errors and Warnings

Status = TRUEStatus = FALSECode = Non-zero

Error Warning

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Errors and Warnings Recommendations

Report errors and warnings with the Simple Error Handler VI Modify Type of Dialog to detect warnings.

Call the Simple Error Handler VI from the top-level VI. Avoid error dialogs in subVIs.

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SummaryQuiz

1. Which of the following will result in a broken run arrow?a) A subVI is broken.b) The diagram includes a divide by zero.

c) A required subVI input is unwired.d) A Boolean terminal is wired to a numeric indicator.

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SummaryQuiz

2. Which of the following are the components and data typesof the error cluster?a) Status: Boolean

b) Error: Stringc) Code: 32-bit integerd) Source: String

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SummaryQuiz Answer

2. Which of the following are the components and data typesof the error cluster?a) Status: Boolean

b) Error: Stringc) Code: 32-bit integerd) Source: String

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SummaryQuiz

3. All errors have negative error codes and all warnings havepositive error codes.

a) True

b) False

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SummaryQuiz Answer

3. All errors have negative error codes and all warnings havepositive error codes.

a) True

b) False

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SummaryQuiz

4. Merge Errors function concatenates error information frommultiple sources.

a) True

b) False

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SummaryQuiz Answer

4. Merge Errors function concatenates error information frommultiple sources.

a) True

b) False

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TOPICS

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Lesson 3

Implementing a VI

A. Front Panel BasicsB. LabVIEW Data TypesC. Documenting Code

D. While LoopsE. For Loops

F. Timing a VIG. Data Feedback in LoopsH. Plotting Data Waveform Chart

I. Case Structures

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A. Front Panel Basics

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Front Panel Basics

Front panel controls and indicators create terminals on theblock diagram.

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B. LabVIEW Data TypesShortcut Menu and Properties Dialog BoxNumeric TypesBoolean Types

String TypesEnums and Other Types

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LabVIEW Data Types

Terminals visually communicate information about the datatype represented

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Shortcut Menus All LabVIEW objects have

associated shortcutmenus.

Use shortcut menu items

to change the look orbehavior of objects. To access the shortcut

menu, right-click theobject.

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Properties Dialog Box All LabVIEW objects have

properties. To access properties,

right-click the object andselect Properties .

Property options aresimilar to shortcut menuoptions.

Select multiple objects tosimultaneously configureshared properties.

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Numerics

Various data typerepresentations: Floating-point Unsigned integers Signed integers

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Numeric Conversion

Coercion dots indicate that LabVIEWconverted the value passed into a node toa different representation. Occurs when a node expects an input with a

different representation. LabVIEW chooses the representation that

uses more bits. Avoid coercion by programmatically

converting to a matching data type.

Coercion Dot

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Booleans Behavior of Boolean

controls is specified by themechanical action.

Boolean have onlyTRUE/FALSE values.

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Mechanical Action of Booleans

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DEMONSTRATION

Mechanical Action of Booleans

Use the PropertiesOperations tab of a Boolean control tolearn about the different switch and latch actions.

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Strings A string is a sequence

of ASCII characters. Strings have various

display styles. Backslash codes Password Hex

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Enums Enums give users a list of

items from which toselect.

Each item represents apair of values. String 16-bit Integer

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Other Data Types

Refer toLabVIEW Help

for complete list of terminal symbolsfor different types of controls and indicators. Dynamic

Stores the information generated or acquired by an Express VI. Path

Stores the location of a file or directory using the standardsyntax for the platform you are using.

Waveform Carries the data, start time, and dt of a waveform.

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DEMONSTRATION

Searching Help for Data Types

Use LabVIEW Helpto learn about LabVIEW data types.


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Documenting Code

VI

Name Description

Front Panel

Label Names Tip Strips Descriptions Free Labels

Block Diagram

Label Names Free Labels Owned

Labels

SubVIDescriptions

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Creating Descriptions and Tip Strips

Use the Properties dialog box to createdocumentation foran object.

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Documenting Block Diagram CodeOwned labels: Explain data contents of wires

and objects. Move with object.

Have transparentbackgrounds. Select Visible ItemsLabel

from the shortcut menu tocreate.

Free labels: Describe algorithms. Have pale yellow backgrounds. Double-click in any open space

to create.

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Exercise 3-1


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GOAL

Exercise 3 1Temperature Warnings VI

Create and document a VI.

Exercise 3-1


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DISCUSSION

Exercise 3 1Temperature Warnings VI

What happens if the Max. Temperature value is lower than theMin. Temperature value?


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D. While LoopsIteration and Conditional TerminalsTunnelsError Checking

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While Loops

LabVIEW While Loop Flowchart Pseudo Code

Repeat (code);

Until Condition met;

End;

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While LoopsIteration terminal Returns number of times loop

has executed. Is zero-indexed.

Conditional terminal Defines when the loop stops. Has two options.

Stop if True

Continue if True

Iteration Terminal Conditional Terminal

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Whil L E Ch ki d E H dli


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While Loops Error Checking and Error HandlingUse an error cluster in a While Loop to stop the While Loop ifan error occurs.

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Exercise 3-2


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GOAL

e c se 3Auto Match VI

DEMONSTRATION

Use a While Loop and an iteration terminal and pass datathrough a tunnel.

Exercise 3-2


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DISCUSSION

Auto Match VI

How many times is theNumber of Iterations indicatorupdated? Why?


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End of Week 2

Week 2 - LabVIEW Student Ambassadors_v1

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