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10 października 2014 Wojciech Kucewicz 1

LabView

Some pictures and slides from LabVIEW Introduction Course


Temperature System


System do pomiaru temperatury


System do pomiaru temperatury


Arrays

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• Collection of data elements that are of same type • One or more dimensions, up to 231 elements per dimension • Elements accessed by their index; first element is index 0

index 10-element array 1.2 3.2 8.2 8.0 4.8 5.1 6.0 1.0 2.5 1.7

0 1 2 3 4 5 6 7 8 9

2D array

Five row by seven column array of 35 elements

0 1 2 3 4 5 6 0 1 2 3 4

Arrays

10 października 2014 Wojciech Kucewicz

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Add Dimension for 2D arrays

1. Select the Array shell from the Controls palette

2. Place data object inside shell

Array Controls and Indicators


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1. Select Array Constant shell from the Array subpalette

2. Place the data object in the array shell

Creating Array Constants


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• Loops can accumulate arrays at their boundaries with auto-indexing

• For Loops auto-index by default

• While Loops output the final value by default

• Right-click on tunnel and enable/disable auto-indexing

Auto-Indexing Wire becomes thicker

Wire remains the same size

Auto-Indexing Disabled

Only one value (last iteration) is passed out of the loop

1D Array

0 1 2 3 4 5


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• Inner loop creates column elements

• Outer loop stacks them into rows

Creating 2D Arrays

1D Array

0 1 2 3 4 5

2D Array


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Auto-Index Input

1. An array input can be used to set the For Loop count terminal

2. Number of elements in the array equals the count terminal input

3. Run arrow not broken


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Temperature symulation


One simulated temperature data value is generated for each call to this subVI. Simulated data repeats in cycles of 100.

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Temperature symulation


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Array Size

Initialize Array

Common Array Functions


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Array Subset

Common Array Functions


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The Build Array Function

Building a higher dimension array

Concatenate Inputs

Appending an element

default


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The Index Array Function

Extracting an Element

Extracting an Element of a Row

Extracting a Row


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Function inputs can be of different types All LabVIEW arithmetic functions are polymorphic

Scalar + Scalar

Array + Scalar

Combination Result

Scalar

Array

Array

Array + Array

Array + Array

Array

Polymorphism


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• Arrays group data elements of the same type. You can build arrays of numeric, Boolean, path, string, waveform, and cluster data types.

• The array index is zero-based, which means it is in the range 0 to n – 1, where n is the number of elements in the array.

• To create an array control or indicator, select an Array on the Controls»Array & Cluster palette, place it on the front panel, and drag a control or indicator into the array shell.

• If you wire an array to a For Loop or While Loop input tunnel, you can read and process every element in that array by enabling auto-indexing.

• By default, LabVIEW enables auto-indexing in For Loops and disables auto-indexing in While Loops.

• Polymorphism is the ability of a function to adjust to input data of different data structures.

Summary



Write to File

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File Input and Output

Four Hierarchy Levels:

High-level File VIs

Intermediate File VIs and Functions

Advanced File Functions subpalette

Express VIs

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File Input and Output

Four Hierarchy Levels:

High-level File VIs


Advanced File Functions subpalette

Express VIs

New arrangement of the File I/O

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The high-level VIs handle all lower level functions transparently and

provide a simplified means of error handling:

Write to Spreadsheet File

Read from Spreadsheet File

Write Characters to File

Read Characters from File

Read Lines from File

High-level File I/O VIs

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Open/ Create/ Replace File

Read and/or Write to File

Close File

Check for Errors

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Write data to File

Open/Create/Replace opens the existing file TEST1.DAT and generates refnum and error cluster Write File writes the data Close File closes the file Simple Error Handler checks for errors

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Reading Data from a File

Open/Create/Replace opens the file

Read File reads the specified number of bytes from the file

Close File closes the file

Simple Error Handler checks for errors


Write data to file

Generate data. Format into string. Write to file.


Write data to file

Generate data. Format into string. Write to file.

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Formatting a Spreadsheet String

Spreadsheets are popular tools for data handling and analysis

There are many formats for spreadsheet data.

One of the most popular is tab-delimited:

Columns are separated by a tab character

Rows are separated by an end-of-line character

Tab End of Line

A spreadsheet yields:

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Creating a Spreadsheet File

Can replace Format Into String and Write File with Format Into File in above example

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Write LabVIEW Measurement File Includes the open, write, close and error handling functions

Handles formatting the string with either a tab or comma delimite

r

Merge Signals function is used to combine data into the dynamic data type

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Use the File I/O VIs and functions located on the Functions»File I/O palette to handle all aspects of file I/O.

When writing to a file, you open, create, or replace a file, write the data, and close the file. Similarly, when you read from a file, you open an existing file, read the data, and close the file.

To access a file through a dialog box, do not wire file path in the Open/Create/Replace File VI.

To write data to a spreadsheet file, you must format the string as a spreadsheet string, which is a string that includes delimiters, such as tabs. Use the Format Into File function to format string, numeric, path, and Boolean data as text and write the text to a file

Summary, cont.


Comunicating with instrument


Communicating with Instruments

You can use LabView to communicate with GPIB Instruments in two ways:

1. The Instrument I/O VIs and functions: which communicate with

the driver-level software for GPIB interface (you can build VIs that use

these VIs and functions directly, but learning and using commands and protocol can be difficult)

2. The LabView Instrument driver: is a set of modular software functions that use the instrument commands or protocol to perform operations with the instrument (eliminate the need to learn the complex, low-level programming commands for each instrument)


Instrument Drivers

The LabView instrument driver library contains instrument drivers for many programmable instruments that use GPIB, VXI or serial

interfaces.

1. You can download drivers from the National Instruments Web site at ni.com.

2. To install the LavView instrument drivers place directory of instrument drivers files in directory: labview\instr.lib.

3. You can access the instrument driver VI’s on the FunctionsInstrument I/O Instrument Drivers palette


Instrument Drivers


Instrument Drivers for K2001


String to Number Convert string read from multimeter into number. The number you can display using waveform chart

Substitute „.” with „,”


Display measurement

Multimeter SubVI


Display options

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Waveform Charts

Selected from the Controls»Graphs and Charts palette

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Wiring to Charts

Single-Plot Chart Multiple-Plot Chart

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Modifying Chart Properties

• Change the appearance

•

• Set the format and precision of the axis

• Choose the plot type

• Edit the scales

• Document the chart


Display option How to configure the appearance of the front panel or SubVI ? It can be done in File VI Properties Category: Windows Appearance


Display option How to configure the appearance of the front panel or SubVI ? It can be done in File VI Properties Category: Windows Appearance

Clik Customize


Display option Example: Read 20x temperature every 0,5 s and display SubVI with Graph


Display option Run different SubVI by pressing buton or key:

The front panel configuration is defined in the File VI properties Windows Appearance

By pressing buttons call different SubVI


Display option Diagram panel:

The program functions: 1. Read temperature 2. Read temperature and save in

the file 3. Read data from file


Display option Diagram panel:

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Customizing Charts and Graphs

Right-click and select Visible Items to view the following items:

1. Plot Legend

2. Digital Display

3. Scrollbar

4. X and Y Scale

5. Graph Palette

6. Scale Legend

Graph Palette

Scale Legend

Zoom Subpalette

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• Selected from the Graph subpalette • Waveform Graph – Plot an array of numbers against their indices • XY Graph – Plot one array against another

Plot Legend (point and line styles)

Graph Palette Scale Legend

Graphs

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Uniform X axis Initial X = 0.0 Delta X = 1.0

Uniform X axis you specify point spacing

Single-Plot Waveform Graphs

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Multiple-Plot Waveform Graphs

Each row is a separate plot: Initial X = 0 Delta X = 1

Each row is a separate plot: Bundle specifies point spacing of the X axis

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• Non-uniform X axis

• Separate X and Y arrays define data points

XY Graphs

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Chart and Graph Use Summary

Use the Context Help window with charts and graphs

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Intensity Plots and Graphs

Useful in displaying terrain, temperature patterns, spectrum analysis, and image processing

Data type is a 2D array of numbers; each number represents a color

Use these options to set and display color mapping scheme

Cursor also adds a third dimension


Display option – Tab Control

Tab Control offers a convenient way to group front panel objects together. You can create Tab Control by selecting Controls Containers Tab Control is wired directly to a Case Structure and the page name correspons to the case.


Display option – Tab Control

Tab Control offers a convenient way to group front panel objects together. You can create Tab Control by selecting Controls Containers Tab Control is wires directly to a Case Structure and the page name correspons to the case.

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The waveform chart is a special numeric indicator that displays one or more plots. The waveform chart has the following three update modes:

1. A strip chart shows running data continuously scrolling from left to right across the chart.

2. A scope chart shows one item of data, such as a pulse or wave, scrolling partway across the chart from left to the right.

3. A sweep works similarly to a scope except it shows the old data on the right and the new data on the left separated by a vertical line.

Waveform graphs and XY graphs display data from arrays.

Right-click a waveform chart or graph or its components to set attributes of the chart and its plots.

Summary

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You can display more than one plot on a graph using the Build Array function and the Bundle function for charts and XY graphs. The graph becomes a multiplot graph when you wire the array of outputs to the terminal.

When you wire data to charts and graphs, use the Context Help window to determine how to wire them.

You can use intensity charts and graphs to plot three-dimensional data. The third dimension is represented by different colors corresponding to a color mapping that you define. Intensity charts and graphs are commonly used in conjunction with spectrum analysis, temperature display, and image processing.

Summary, cont.


Property node


Property Nodes Property Nodes in LabView are very powerful and have many uses. You can create Property Nodes by selecting Create Property Node It creates a new node with the same name as object. Property Node has one terminal: for reading or writing property.


Property Nodes


Cluster

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Clusters

1. Data structure that groups data together

2. Data may be of different types

3. Analogous to struct in C or a record in Pascal

4. Elements must be either all controls or all indicators

5. Thought of as wires bundled into a cable

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1. Select a Cluster shell from the Array & Cluster subpalette

Cluster Controls and Indicators

2. Place objects inside the shell

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Creating Cluster Constants

1. Select Cluster Constant shell from the Cluster subpalette

2. Place objects in the Cluster shell


Cluster

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Cluster Order

1. Elements have a logical order (start with 0) 2. To change order, right-click the border and select

Reorder Controls in Cluster...

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Using Clusters to Pass Data to SubVIs

Use clusters to pass several values to one terminal

Overcomes 28-terminal limit

Simplifies wiring

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Cluster Functions - Bundle Bun

dle

Bun

dle

By N

ame

Create new cluster Modify existing cluster

Must have an existing cluster to use this function.

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Cluster Functions - Unbundle

Unbundle Unbundle By Name

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Error Cluster

Use the error in and error out clusters in each VI you use or build to handle errors in the VI.

The error clusters located on the Controls»Array & Cluster palette include the components of information shown

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Error Cluster Details

1. Status is a Boolean value that reports TRUE if an error occurred. Most VIs, functions, and structures that accept Boolean data also recognize this parameter.

2. Code is a signed 32-bit integer that identifies the error numerically. A non-zero error code coupled with a status of FALSE signals a warning rather than a fatal error.

3. Source is a string that identifies where the error occurred.

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Error Handling with Clusters

1. LabVIEW does not handle errors automatically. In LabVIEW, you can make these error handling decisions on the block diagram of the VI.

2. Error handling in LabVIEW follows the dataflow model. Just as data flow through a VI, so can error information.

3. Wire the error information from the beginning of the VI to the end.

Error Cluster

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Simple Error Handler

Use the Simple Error Handler to handle the error at the end of the execution flow. The Simple Error Handler is located on the Functions»All Functions»Time and Dialog palette. Wire the error cluster to the Error In (no error) input.

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Using While Loops for Error Handling

You can wire an error cluster to the conditional terminal of a While Loop to stop the iteration of the While Loop.

Only the TRUE or FALSE value of the status parameter of the error cluster is passed to the terminal.

When an error occurs, the While Loop stops.

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• Clusters group data elements of mixed types. A cluster cannot contain a mixture of controls and indicators.

• To create a cluster control or indicator, select a cluster on the Controls»Array & Cluster palette, place it on the front panel, and drag controls or indicators into the cluster shell.

• Use the Cluster functions located on the Functions»All Functions»Cluster palette to create and manipulate clusters.

• Error checking tells you why and where errors occur.

• The error cluster reports the status, code and source of the error.

• Use the error cluster controls and indicators to create error inputs and outputs in subVIs.

Summary

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String

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A string is a sequence of displayable or - characters (ASCII) Many uses — displaying messages, instrument control, file I/O String control/indicator is in the Controls»String subpalette

Strings

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String Display Modes

Normal display Password display

\ code display Hex display

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Concatenate Strings (spaces here)

String Length

String Functions

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String Functions

String Subset

Match Pattern

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Converting Numerics to Strings: Build String

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Converting Strings to Numerics: Scan From String

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Edit Format String

Scan From String Function

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Strings group sequences of ASCII characters. Use the string control and indicator located on the Controls»String & Path palette to simulate text entry boxes and labels.

Use the String functions located on the Functions»String palette to edit and manipulate strings on the block diagram.

Use the Format Into String function and the Build String Express VI to convert a numeric to a string.

Use the Scan From String function to convert a string to a numeric.

Right-click the Format Into String or Scan From String function and select Edit Format String or Edit Scan String from the shortcut menu to create or edit a format string.

Summary

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Use the File I/O VIs and functions located on the Functions»File I/O palette to handle all aspects of file I/O.

When writing to a file, you open, create, or replace a file, write the data, and close the file. Similarly, when you read from a file, you open an existing file, read the data, and close the file.

To access a file through a dialog box, do not wire file path in the Open/Create/Replace File VI.

To write data to a spreadsheet file, you must format the string as a spreadsheet string, which is a string that includes delimiters, such as tabs. Use the Format Into File function to format string, numeric, path, and Boolean data as text and write the text to a file

Summary, cont.

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