nis labview

NISARG MARATHA KASHYAP SHAH

LabVIEW

Part 1: Introduction

Part 2: The LabVIEW Environment

Part 3: Audio-Visual Demo

Part 4: Applications, Advantages and Future of LabVIEW

Part 1

PART 1 : Introduction

LabVIEW – Laboratory Virtual Instrument Engineering Workbench

It is a platform and development environment for a visual programming language from National Instruments.

The purpose of such programming is automating the usage of processing and measuring equipment in any laboratory setup. LabVIEW is commonly used for data acquisition, instrument control, and industrial automation on a variety of platforms including Microsoft Windows, various versions of UNIX, Linux, and Mac OS X. The latest version of LabVIEW is version LabVIEW 2011, released in August 2011.

Design Signal and Image Processing Embedded System Programming

(PC, DSP, FPGA, Microcontroller) Simulation and Prototyping And more…

Control Automatic Controls and Dynamic Systems Mechatronics and Robotics And more…

Measurements Circuits and Electronics Measurements and Instrumentation And more…

Features of LabVIEW 7.1

What is Data Acquisition and it’s use ?

Traditional Experiments – signals from sensors are sent to analog or digital meters, read by the experimenter, and recorded by hand.

In automated data acquisition systems the sensors transmit a voltage or current signal directly to a computer via a data acquisition board.

Software such as LabVIEW controls the acquisition and processing of such data.

The benefits of automated systems are many: Improved accuracy of recording. Increased frequency with which measurements

can be taken.

Graphical programming language & Data flow

LabVIEW relies on graphical symbols rather than textual language to describe programming actions.

The principle of dataflow, in which functions execute only after receiving the necessary data, governs execution in a straightforward manner.

How does LabVIEW work?

• LabVIEW programs are called:Virtual Instruments (VIs)

because their appearence and operation imitate actual instruments.

• However, they are analogous to main programs, functions and subroutines from popular language like C, Fortran, Pascal, …

What does a VI look like?

In LabVIEW you can create or use “virtual instruments” (VI) for data acquisition. A VI allows your computer screen to act as an actual laboratory instrument with characteristics tailored to your particular needs.

You can also use built-in examples, or use standard templates for setting up your data acquisition input channels.

A VI has three main parts:

• The front panel: an interactive user interface of a VI, so named because it can simulates the front panel of a physical instrument.

• The block (or wiring) diagram:• It is the VI’s source code, constructed in LabVIEW’s • graphical programming language, G. It is the actual• executable program.

• Subroutine in the block diagram of VI.

• Icon/connector

Part 2: The LabVIEW Environment

Front PanelEvery user created VI has a front panel that contains the graphical interface with which a user interacts. The front panel can house various graphical objects ranging from simple buttons to complex graphs. Various options are available for changing the look and feel of the objects on the front panel to match the needs of any application.

Block diagramNearly every VI has a block diagram containing some kind of program logic that serves to modify data as it flows from sources to sinks. The block diagram houses a pipeline structure of sources, sinks, VIs, and structures wired together in order to define this program logic. Most importantly, every data source and sink from the front panel has its analog source and sink on the block diagram. This representation allows the input values from the user to be accessed from the block diagram. Likewise, new output values can be shown on the front panel by code executed in the block diagram.

Controls• The most common form of a data source in LabVIEW is a control. This element

appears as some type of graphical element on the front panel of a VI that can receive input from a user or even another VI. As stated previously, any data source also has an analog symbol that appears on the block diagram so that its value can be read and used in the code pipeline. Controls make no exception to this rule.

• Every control has an associated data type that determines what kind of data flows from it on the block diagram.

Palettes• Front panel controls and indicators as well as block diagram VIs are available

from a palettes visible depending on what window is currently active in the LabVIEW environment. These palettes have their contents separated into sub-categories containing controls, indicators, and VIs.

Figure 4: Typical top-level block diagram and front panel palettes.Typical top-level block

diagram and front panel palettes.

Front PanelsSimply put, the front panel is the window through which the user interacts with the program.• When you run a VI, you must

have the front panel open so that you can input data to the executing program.

• The front panel is where you see your program’s output.The front panel is primarily a combination of controls and

indicators.

Control? or Indicator?

Controls = Inputs from the user = Source Terminals

Indicators = Outputs to the user = Destinations

Block DiagramsThe block diagram window holds the graphical source code of a LabVIEW VI – it is the actual executable code• You construct the block

diagram by wiring together objects that perform specific functions.

• The various components of a block diagram are terminals, nodes and wires.

TerminalsWhen you place a control (or indicator) on the FRONT PANEL

LabVIEW automatically creates a correspondingcontrol (or indicator) terminal on the BLOCKDIAGRAM

Control or Indicator Terminal?

Control terminals havethick borders

Indicator terminals havethin borders

Deleting Block Diagram Terminals

• By default, you cannot delete a block diagram terminal that belongs to a control (or indicator).

• The terminal disappears only when you delete its corresponding control (or indicator) on the FRONT PANEL.

Wires

A LabVIEW VI is held together by wires connecting nodes and terminals; they deliver data from one source terminal to one or more destination terminals.

Basic wires used in block diagrams

and corresponding typesEach wire has different style or color, depending on the data type that flows through the wire:

Scalar 1D array 2D array Color

Floating-point number

orange

Integer number blue

Boolean green

String pink

6hrs

VI Front Panel

Front Panel Toolbar

GraphLegend

BooleanControl

WaveformGraph

Icon

PlotLegend

ScaleLegend

VI Block Diagram

Wire Data

GraphTerminal

SubVI

While LoopStructure

Block Diagram Toolbar Divide

Function

Numeric Constant

Timing Function

Boolean Control Terminal

Controls and Functions Palettes

Controls Palette (Front Panel Window)

Functions Palette (Block 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

Resize front panel objects

Execution Highlighting Button Step Into Button

Step Over Button

Step Out Button

Additional Buttons on the Diagram Toolbar

Status Toolbar

The Run Button• The Run button, which looks like an

arrow, starts VI execution when you click on it

• It changes appearance when a VI is actually running.

• When a VI won’t compile, the run button is broken

Open and Run a Virtual Instrument

Example finder

ControlTerminals

Block Diagram Window

Front Panel Window

Indicator Terminals

Creating a VI

Help Options

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

Debugging Techniques

• Finding Errors

• Execution Highlighting

• Probe

Click on broken Run buttonWindow showing error appears

Click on Execution Highlighting button; data flow is animated using bubbles. Values are displayed on wires.

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

You can also select Probe tool from Tools palette and click on wire

Part 3

• Shortcuts• Ctrl + T //tile windows• <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)•

– Simple program (simple addition, multiplication etc…)

– Loops (from video)– Charts graphs (from video)– Case structures (from video) – Tools palette (from video)– Hardware implementation (from video)– Data types, highlight execution, data acquisition,

arrays, debugging tools etc…

Hardware implementation

Data Types

arrays

Data acquisition

Part 3 - B

Section II – SubVIs

• What is a subVI?• Making an icon and

connector for a subVI

• Using a VI as a subVI

Block Diagram NodesIcon Expandable Node Expanded Node

• Function Generator VI• Same VI, viewed three different ways• Yellow field designates a standard VI• Blue field designates an Express VI

SubVIs

• A SubVI is a VI that can be used within another VI• Similar to a subroutine• Advantages

– Modular– Easier to debug– Don’t have to recreate code– Require less memory

Icon and Connector

• An icon represents a VI in other block diagrams

• A connector shows available terminals for data transfer

Icon

Connector

Terminals

SubVIsSub VIs

Steps to Create a SubVI

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

Create the Icon• Right-click on the icon in the

block diagram or front panel

Create the Connector

Right click on the icon pane (front panel only)

Assign Terminals

Save 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 SubVI into a Top Level VI

Accessing user-made subVIsFunctions >>All Functions >> Select a VI

Or Drag icon onto target diagram

Section III – Data Acquisition

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

Computer

DAQ Device

Terminal Block

Cable

Sensors

Data Acquisition in LabVIEW

Traditional NI-DAQSpecific VIs for performing:• Analog Input• Analog Output• Digital I/O• Counter operations

NI-DAQmxNext generation driver: • VIs for performing a

task• One set of VIs for all

measurement types

DAQ – Data AcquisitionTemperature Acquisition using the DAQ Assistant

Data Acquisition Terminology

• Resolution - Determines How Many Different Voltage Changes Can Be Measured– Larger Resolution More Precise Representation

of Signal• Range - Minimum and Maximum Voltages

– Smaller range More Precise Representation of Signal

• Gain - Amplifies or Attenuates Signal for Best Fit in Range

Hardware Connections

BNC-2120

SCB-68

NI-ELVIS

SC-2075

Section IV – Loops and Charts

• For Loop• While Loop• Charts• Multiplots

Loops• While Loops

– Have Iteration Terminal– Always Run at least Once– Run According to

Conditional Terminal

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

Count Terminal

Loops (cont.)1. Select the loop 2. Enclose code to be repeated

3. Drop or drag additional nodes and then wire

Charts

Waveform chart – special numeric indicator that can display a history of values

Controls >> Graph Indicators >> Waveform Chart

Wiring Data into Charts

Single Plot Charts Multiplot Charts

Section 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 PanelFrom the Controls >> All Controls >> Array and

Cluster subpalette, select the Array Shell

Drop it on the screen.

Adding an Array (cont.)Place data object into shell (i.e. Numeric Control)

Creating an Array with a Loop• Loops accumulate arrays at their boundaries

Creating 2D Arrays

File I/OFile I/O – passing data to and from files

- Files can be binary, text, or spreadsheet

- Write/Read LabVIEW Measurements file (*.lvm)

Writing to LVM file Reading from LVM file

Write LabVIEW Measurement File

• Includes the open, write, close and error handling functions

• Handles formatting the string with either a tab or comma delimiter

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

Section VI – Array Functions & Graphs

• Basic Array Functions• Use graphs• Create multiplots with graphs

Array Functions – Basics

Functions >> All functions>> Array

Array Functions – Build Array

Graphs• Selected from the Graph palette of Controls

menuControls>>All Controls>>Graphs

Waveform Graph – Plot an array of numbers against their indicesExpress XY Graph – Plot one array against anotherDigital Waveform Graph – Plot bits from binary data

Graphs

Right-Click on the Graph and choose Propertiesto Interactively Customize

Section VII – Strings, Clusters, & Error Handling

• Strings• Creating Clusters• Cluster Functions• Error I/O

Strings

•A string is a sequence of displayable or nondisplayable characters (ASCII)

•Many uses – displaying messages, instrument control, file I/O

•String control/indicator is in the Controls »Text Control or Text Indicator

Clusters

• 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

Creating a Cluster1. Select a Cluster shell

Controls >> All Controls >> Array & Cluster

2. Place objects inside the shell

Cluster Functions• In the Cluster subpalette of the Functions>>All functions palette• Can also be accessed by right-clicking on the cluster terminal

Bundle

(Terminal labels reflect data type)

Bundle By Name

Cluster Functions

Unbundle

Unbundle By Name

Unbundled cluster in the diagram

Error Clusters

• 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 Handling Techniques• Error information is passed from one subVI to the next• If an error occurs in one subVI, all subsequent subVIs

are not executed in the usual manner• Error Clusters contain all error conditions• Automatic Error Handling

error clusters

Section VIII - Case & Sequence Structures, Formula Nodes

Case Structures• 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

Functions >> Execution control

Sequence Structures• In the Execution Control subpalette of Functions

palette• Executes diagrams sequentially• Right-click to add new frame

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

Section IX – Printing & Documentation

• Print From File Menu to Printer, HTML, Rich Text File

• Programmatically Print Graphs or Front Panel Images

• Document VIs in VI Properties » Documentation Dialog

• Add Comments Using Free Labels on Front Panel & Block Diagram

Printing• File » Print… Gives Many Printing Options

– Choose to Print Icon, Front Panel, Block Diagram, VI Hierarchy, Included SubVIs, VI History

• Print Panel.vi (Programmatically Prints a Front Panel) – Functions » All Functions » Application Control

• Generate & Print Reports (Functions » Output » Report)

Documenting VIs

• VI Properties » Documentation– Provide a Description and Help Information for a VI

• VI Properties » Revision History– Track Changes Between Versions of a VI

• Individual Controls » Description and Tip…– Right Click to Provide Description and Tip Strip

• Use Labeling Tool to Document Front Panels & Block Diagrams

Section X – Basic Programming Architecture

• Simple VI Architecture• General VI Architecture• State Machine Architecture

Simple VI Architecture• Functional VI that produces results when run

– No “start” or “stop” options– Suitable for lab tests, calculations

• Example: Convert C to F.vi

General VI Architecture• Three Main Steps

– Startup– Main Application– Shutdown

State Machine Architecture

• Advantages– Can go from any state from any

other– Easy to modify and debug

• Disadvantages– Can lose events if two occur at the

same timeStates:0: Startup1: Idle2: Event 13: Event 24: Shutdown

Section XI – Remote Front Panels

• View & Control LabVIEW Front Panels from a Web Browser

• Requires no programming• Remote clients see “live” 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, it can be reopened and customized in any HTML editor

Remote Front Panels - Resources• NI Developer Zone

(zone.ni.com)– Search for Remote

Front Panel– Tutorials & Instructions

Are Available for Download

– Information on Incorporating Web Cameras into Remote Panel Applications

110

Serial Communication

• Popular means of communication between computer and peripheral device

• Data sent one bit at a time across the cable• Used for low transfer rates or long distances• Only a cable is needed since most computers have at

least one available serial port

RS-232 Instrument

RS-232 Cable

PC SerialPort

111

Serial Hardware Connection

• RS-232– DCE or DTE configurations– 9-pin or 25-pin

• RS-422– DCE or DTE– 8-pin

• RS-485– Multidrop

Pin DTE DCE

1 DCD Input Output2 RxD I O3 TxD O I4 DTR O I5 Com - -6 DSR I O7 RTS O I8 CTS I O9 RI I O

112

Serial Communication

Terminology• Baud rate – bits per second• Data bits – inverted logic and LSB first• Parity – optional error-checking bit• Stop bits – 1, 1.5, or 2 inverted bits at data end• Flow control – hardware and software handshaking options

113

Using the Instrument I/O Assistant with Serial

• Select COMX as the instrument address

• Use the I/O Assistant as done with GPIB

114

Summary

• LabVIEW can communicate with any instrument that connects to your computer if you know the interface type

• Use the Measurement & Automation Explorer (MAX) to detect, configure, and test your GPIB interface and instruments

• Use the Instrument I/O Assistant for easy and fast GPIB and serial programming.

• An instrument driver eliminates the need for your to have detailed knowledge of the specific strings used by an instrument

• Instrument Library – more than 2000 instruments supported• Instrument driver VIs share a common hierarchy and come

with an example to help you get started

Part 4

ad

disad

app

future

??

ref

ty