Introduction to LabVIEW Adapted from NI’s 3-Hour Hands-On Tour

Introduction to LabVIEW Adapted from NI’s 3-Hour Hands-On Tour

Course Goals Become comfortable with the LabVIEW environment and data flow execution Ability to use LabVIEW to solve problems LabVIEW Concepts – Acquiring, saving and loading data – Find and use math and complex analysis functions – Work with data types, such as arrays and clusters – Displaying and printing results

Open and Run LabVIEW Start»All Programs»National Instruments LabVIEW 8.0 » Startup Screen: Start from a Blank VI: New»Blank VI or Start from an Example: Examples»Find Examples

LabVIEW Programs Are Called Virtual Instruments (VIs) Each VI has 2 Windows Front Panel User Interface (UI) – Controls Inputs – Indicators Outputs Block Diagram Graphical Code – Data travels on wires from controls through functions to indicators – Blocks execute by Dataflow

Controls Palette (Place items on the Front Panel Window) (Controls & Indicators) Control: Numeric Customize Palette View Indicator: Numeric Slide

Functions (and Structures) Palette (Place items on the Block Diagram Window) Structure: While Loop

Status Toolbar Run Button Continuous Run Button Abort Execution Additional Buttons on the Diagram Toolbar Execution Highlighting Button Retain Wire Values Button Step Function Buttons

Demonstration 1: Creating a VI Front Panel Window Graph Indicator Block Diagram Window Output Terminal Boolean Control Input Terminals

Dataflow Programming Block diagram execution – Dependent on the flow of data – Block diagram does NOT execute left to right* Node executes when data is available to ALL input terminals Nodes supply data to all output terminals when done * However, Sequence structure forces flow

Debugging Techniques Finding Errors Click on broken Run button. Window showing error appears. Execution Highlighting Click on Execution Highlighting button; data flow is animated using bubbles. Values are displayed on wires. Probes 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.

Context Help Window Help»Show Context Help, press the Ctrl H keys Hover cursor over object to update window Additional Help – Right-Click on the VI icon and choose Help, or – Choose “Detailed Help.” on the context help window

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) Tools»Options – Set Preferences in LabVIEW VI Properties–Configure VI Appearance, Documentation, etc.

Section II – Elements of Typical Programs A. Functions and SubVIs Types of Functions Creating Custom Functions (SubVI) Functions Palette & Searching B. Loops While Loop For Loop C. Decision Making and File IO Case Structure Select (simple If statement) File I/O

3 Types of Functions (from the Functions Palette) Express VIs: interactive VIs with configurable dialog page (blue border) Standard VIs: modularized VIs customized by wiring (customizable) Functions: fundamental operating elements of LabVIEW; no front panel or block diagram (yellow)

What Types of Functions are Available? Input and Output – – – – Signal and Data Simulation Acquire and Generate Real Signals with DAQ Instrument I/O Assistant (Serial & GPIB) ActiveX for communication with other programs Analysis – – – – Signal Processing Statistics Advanced Math and Formulas Continuous Time Solver Storage – File I/O Express Functions Palette

Searching for Controls, VIs, and Functions Palettes are filled with hundreds of VIs Press the search button to index the all VIs for text searching Click and drag an item from the search window to the block diagram Double-click an item to open the owning palette

Create SubVI Enclose area to be converted into a subVI. Select Edit»Create SubVI from the Edit Menu.

LabVIEW Functions and SubVIs operate like Functions in other languages Function Pseudo Code Calling Program Pseudo Code function average (in1, in2, out) { out (in1 in2)/2.0; } main { average (in1, in2, pointavg) } SubVI Block Diagram Calling VI Block Diagram

Loops While Loop While Loops – i terminal counts iteration – Always runs at least once – Runs until stop condition is met For Loops – i terminal counts iterations – Run according to input N of count terminal For Loop

Drawing a Loop 2. Enclose code to be repeated 1. Select the structure 3. Drop or drag additional nodes and then wire

Shift Register – Access Previous Loop Data Available at left or right border of loop structures Right-click the border and select Add Shift Register Right terminal stores data on completion of iteration Left terminal provides stored data at beginning of next iteration Initial Value Before Loop Begins Value 3 First Iteration Second Iteration Last Iteration

How Do I Make Decisions in LabVIEW? 1. Case Structures 2. Select (a) (c) (b)

File I/O File 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

File I/O File I/O – passing data to and from files Regular VIs allow writing arrays of numeric data to tabdelimited spreadsheet files

Section III – Presenting your Results A. Displaying Data on the Front Panel Controls and Indicators Graphs and Charts Loop Timing B. Signal Processing MathScript Arrays Clusters Waveforms

What Types of Controls and Indicators are Available? Numeric Data – Number input and display – Analog Sliders, Dials, and Gauges Boolean Data – Buttons and LEDs Array & Matrix Data – – – – – – Numeric Display Chart Graph XY Graph Intensity Graph 3D graph: point, surface, and model Decorations – Tab Control – Arrows Other – Strings and text boxes – Picture/Image Display – ActiveX Controls Express Controls Palette

Charts – Add 1 data point at a time with history Waveform chart – special numeric indicator that can display a history of values Chart updates with each individual point it receives Functions»Express»Graph Indicators»Chart

Graphs – Display many data points at once Waveform graph – special numeric indicator that displays an array of data* Graph updates after all points have been collected May be used in a loop if VI collects buffers of data Functions»Express»Graph Indicators»Graph *Uniformly spaced on x-axis

Graphs – Display many data points at once XY graph – special numeric indicator that displays an array of data that isn’t necessarily spaced equally in time Graph updates after all points have been collected Functions»Express»Graph Indicators»XY Graph Automatically converts float to dynamic

Building Arrays with Loops (Auto-Indexing) Loops can accumulate arrays at their boundaries with auto-indexing For Loops auto-index by default While Loops output only the final value by default Right-click tunnel and enable/disable autoindexing Auto-Indexing Enabled Wire becomes thicker 1D Array 012345 Auto-Indexing Disabled Wire remains the same size 5 Only one value (last iteration) is passed out of the loop

Creating an Array (Step 1 of 2) From the Controls»Modern»Array, Matrix, and Cluster subpalette, select the Array icon. Drop it on the Front Panel.

Create an Array (Step 2 of 2) 1. Place an Array Shell. 2. Insert datatype into the shell (i.e. Numeric Control).

How Do I Time a Loop? 1. Loop Time Delay Configure the Time Delay Express VI for seconds to wait each iteration of the loop (works on For and While loops). 2. Timed Loops Configure special timed While loop for desired dt. Time Delay Timed Loop

Control & Indicator Properties Properties are characteristics or qualities about an object Properties can be found by right clicking on a Control or Indicator Properties Include: – Size – Color – Plot Style – Plot color Features include: – Cursors – Scaling

Review of Data Types Found in LabVIEW

Section IV – Advanced Data Flow Topics (optional) A. Additional Data types Cluster B. Timing Control Sequences C. Large Application Development Navigator Window LabVIEW Projects

Introduction to 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 Order is important

Creating a Cluster 1. Select a Cluster shell. 2. Place objects inside the shell. Controls»Modern»Array, Matrix & Cluster

Cluster Functions In the Cluster & Variant subpalette of the Programming palette Can also be accessed by right-clicking the cluster terminal (Terminal labels reflect data type) Bundle Bundle By Name

Using Arrays and Clusters with Graphs The Waveform Datatype contains 3 pieces of data: t0 Start Time dt Time between Samples Y Array of Y magnitudes Two ways to create a Waveform Cluster: Build Waveform (absolute time) Cluster (relative time)

Sequences Sequences (Stacked or Flat) forces data to flow in a specific order. Will not advance to next frame until every element in current frame has been completed. Flat Sequence Stacked Sequence Currently showing from 1 of 0 3 Previously Defined Local, Currently Defined Local, Undefined Local (accessible now) (accessible in later frames) (inaccessible)

LabVIEW Navigation Window Shows the current region of view compared to entire Front Panel or Block Diagram Great for large programs * Organize and reduce program visual size with subVIs

LabVIEW Project Group and organize VIs Hardware and I/O management Manage VIs for multiple targets Build libraries and executables Manage large LabVIEW applications Enable version tracking and management (LabVIEW»Project»New)

Additional Resources NI Academic Web & Student Corner – http://www.ni.com/academic Connexions: Full LabVIEW Training Course – www.cnx.rice.edu – Or search for “LabVIEW basics” LabVIEW Certification – LabVIEW Fundamentals Exam (free on www.ni.com/academic) – Certified LabVIEW Associate Developer Exam (industry recognized certification ) Get your own copy of LabVIEW Student Edition – www.ni.com/academic or f d te a d Up VIEW 8 La b By Robert H Bishop. Published by Prentice Hall.

The LabVIEW Certification Program Architect Mastery of LabVIEW Expert in large application development Skilled in leading project teams Certified LabVIEW Architect Developer Advanced LabVIEW knowledge and application development experience Project management skills Certified LabVIEW Developer Associate Developer Proficiency in navigating LabVIEW environment Some application development experience Fundamentals Exam Pre-Certification Skills Test Certified LabVIEW Associate Developer Free On-Line Fundamentals Exam

Electronics Workbench and Multisim World’s most popular software for learning electronics 180,000 industrial and academic users Products include: – – – – – Multisim: Simulation and Capture Multi-MCU: Microcontroller Simulation MultiVHDL: VHDL Simulation Ultiboard: PCB Layout Electronics CBT: Computer-based training Low cost student editions available www.electronicsworkbench.com

Multisim Integrated with LabVIEW 1. Create Schematic 4. PCB Layout 2. Virtual Breadboard 5. Test 3. Simulate 6. Compare

Your Next Step Take the free LabVIEW Fundamentals Exam at ni.com/academic Your first step to become LabVIEW Certified!

The Virtual Instrumentation Approach

LabVIEW Graphical Development System Graphical Programming Environment Compile code for multiple OS and devices Useful in a broad range of applications

Virtual Instrumentation Applications Design – Signal and Image Processing – Embedded System Programming A single graphical development platform (PC, DSP, FPGA, Microcontroller) – Simulation and Prototyping Design – And more Control – Automatic Controls and Dynamic Systems – Mechatronics and Robotics – And more Measurements – Circuits and Electronics – Measurements and Instrumentation – And more Prototype Deploy

The NI Approach – Integrated Hardware Platforms PXI Modular Instrumentation High-Speed High-Resolution Multifunction Dynamic Instrument Digitizers and DMMs Data Acquisition Signal Acquisition Control Digitizers Signal Conditioning and Switching Unit Under Test Laptop PC Desktop PC Digital I/O Counter/ Timers Machine Vision Motion Control Distributed I/O and Embedded Control PDA

Section I – LabVIEW Environment A. Getting Data into your Computer Data Acquisition Devices – NI-DAQ – Simulated Data Acquisition – Sound Card B. LabVIEW Environment Front Panel / Block Diagram Toolbar /Tools Palette C. Components of a LabVIEW Application Creating a VI Data Flow Execution D. Additional Help Finding Functions Tips for Working in LabVIEW

A. Setting Up Your Hardware Data Acquisition Device (DAQ) Track A – Actual USB, PCI, or PXI Device – Configured in MAX Simulated Data Acquisition Device (DAQ) – Software simulated at the driver level – Configured in MAX Sound Card Track C – Built into most computers Track B

What type of device should I use? Sound Card* NI USB DAQ NI PCI DAQ Instruments* AI Bandwidth 8–44 KS/s 10–200 KS/s 250 K–1.2 Ms/s 20kS/s–2 GS/s Accuracy 12–16 bit 12–16 bit 14–18 bit 12–24 bit Portable x x — some AI Channels 2 8–16 16–80 2 AO Channels 2 1–2 2–4 0 AC or DC AC AC/DC AC/DC AC/DC Triggering — x x x Calibrated — x x x * The above table may not be representative of all device variations that exist in each category

What is MAX? MAX stands for Measurement & Automation Explorer. MAX configures and organizes all your National Instruments DAQ, PCI/PXI instruments, GPIB, IMAQ, IVI, Motion, VISA, and VXI devices. Used for configuring and testing devices. Icon Found on Windows Desktop

Exercise 1 – Setting Up Your Device Track A Use Measurement and Automation Explorer (MAX) to: – Configure and test your Data Acquisition (DAQ) device

Exercise 1 – Setting Up Your Device Track B Use Measurement and Automation Explorer (MAX) to: – Configure and test your Simulated Data Acquisition (DAQ) device

Exercise 1 – Setting Up Your Device Use Windows to: – Verify your Sound Card Un-Mute Microphone Track C

Exercise 2 – Acquiring a Signal with DAQ Use a LabVIEW template to: – Acquire a signal from your DAQ device This exercise should take 15 minutes. Track A&B

Track C Exercise 2 – Acquiring a Signal with the Sound Card Use LabVIEW to: – Acquire a signal from your sound card This exercise should take 15 minutes.

Exercise 3.1 – Analysis Track A,B,&C Use LabVIEW Express VIs to: – Simulate a signal and display its amplitude and frequency This exercise should take 15 minutes.

Exercise 3.2 – Analysis Track A&B Use LabVIEW Express VIs to: – Acquire a signal and display its amplitude and frequency This exercise should take 15 minutes.

Exercise 3.2 – Analysis Track C Use LabVIEW Express VIs to: – Acquire a signal and display its amplitude and frequency This exercise should take 15 minutes.

Track A,B,C Exercise 3.3 – Decision Making and Saving Data Use a case structure to: – Make a VI that saves data when a condition is met This exercise should take 15 minutes.

File I/O Programming Model – Under the hood Open/ Create/ Replace File Read and/or Write to File Close File Check for Errors

Exercise 4.1 – Manual Analysis Track A,B,&C Use the cursor legend on a graph to: – Verify your frequency and amplitude measurements This exercise should take 15 minutes.

Textual Math in LabVIEW Integrate existing scripts with LabVIEW for faster development Interactive, easy-to-use, hands-on learning environment Develop algorithms, explore mathematical concepts, and analyze results using a single environment Freedom to choose the most effective syntax, whether graphical or textual within one VI Supported Math Tools: MathScript script node Mathematica software Maple software MathSoft software MATLAB software Xmath software MATLAB is a registered trademark of The MathWorks, Inc.

Math with the MathScript Node Implement equations and algorithms textually Input and Output variables created at the border Generally compatible with popular m-file script language Terminate statements with a semicolon to disable immediate output (Functions»Programming» Structures»MathScript) Prototype your equations in the interactive MathScript Window.

The Interactive MathScript Window Rapidly develop and test algorithms Share Scripts and Variables with the Node View /Modify Variable content in 1D, 2D, and 3D Output Window Variable Workspace View/Modify Variable Contents User Commands m-file Script (LabVIEW»Tools»MathScript Window)

Exercise 4.2 – Using MathScript Track A,B,&C Use the MathScript Node and Interactive Window to process the acquired signal (logarithmic decay) in the MathScript and save the script. This exercise should take 25 minutes.

Exercise 5 – Apply What You Have Learned This exercise should take 20 minutes. Track A,B,&C

Local Variables Local Variables allow data to be passed between parallel loops. A single control or indicator can be read or written to from more than one location in the program – Local Variables break the dataflow paradigm and should be used sparingly