nis labview
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An award winning software for engineers & data acquistition, signal processing ...TRANSCRIPT
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
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