Virtual Instruments with LabVIEW

Transcription

1 Telemark University College Department of Electrical Engineering, Information Technology and Cybernetics Virtual Instruments with LabVIEW HANS-PETTER HALVORSEN, Faculty of Technology, Postboks 203, Kjølnes ring 56, N-3901 Porsgrunn, Norway. Tel: Fax:

2 2 Virtual Instruments with LabVIEW Introduction LabVIEW (short for Laboratory Virtual Instrumentation Engineering Workbench) is a platform and development environment for a visual programming language from National Instruments. The graphical language is named "G". Originally released for the Apple Macintosh in 1986, LabVIEW is commonly used for data acquisition, instrument control, and industrial automation on a variety of platforms including Microsoft Windows, various flavors of UNIX, Linux, and Mac OS X. The latest version of LabVIEW is version LabVIEW Visit National Instruments at LabVIEW programs are called Virtual Instruments, or VIs, because their appearance and operation imitate physical instruments, such as oscilloscopes and multimeters. LabVIEW contains a comprehensive set of tools for acquiring analyzing, displaying, and storing data, as well as tools to help you troubleshoot your code. Here we will go through some simple LabVIEW examples in order to learn basic LabVIEW programming. For more background information about LabVIEW, see the tutorial Introduction to LabVIEW.

3 3 Virtual Instruments with LabVIEW You may also want to take a closer look at the Interactive Training called LabVIEW Starter :

4 4 Virtual Instruments with LabVIEW Front Panel and Block Diagram In this task you will learn to create a simple user interface in LabVIEW and how to create the code for it. When you open a blank VI, an untitled front panel window appears. This window displays the front panel (the user interface) and is one of the two LabVIEW windows you use to build a VI. The other window contains the block diagram (the code). In LabVIEW, you build a user interface, or front panel, with controls and indicators. Controls are knobs, push buttons, dials, and other input devices. Indicators are graphs, LEDs, and other displays. Front Panel Example: If you right-click on the Front Panel, the Controls palette appears:

5 5 Virtual Instruments with LabVIEW Block Diagram Example: If you right-click on the Front Panel, the Functions palette appears:

6 6 Virtual Instruments with LabVIEW Task 1: Create a simple Calculator Step 1: Create the following front panel (user interface) in LabVIEW:

7 7 Virtual Instruments with LabVIEW Step 2: Create the block diagram (code) to make the program work as expected. Step 3: Push the Run button to do the calculations. [End of Task] Loops and Structures Like other programming languages have LabVIEW different Loops and structures available. The different Loops and Structures available are located in the Structures sub palette in the Functions palette on the Block Diagram. Task 2: Using While Loops Step 1: Create the following front panel: Step 2: Create the block diagram for the program using a While Loop. The Date and Time strings should be updated every second.

8 8 Virtual Instruments with LabVIEW You may want to use the following built-in functions in LabVIEW: [End of Task] Task 3: Create an advanced Calculator Create the following program: You need to use a While Loop and an Event Structure inside the While loop to solve the problem. The Event structure is used to respond to buttons clicks, such as when the user clicks the Calculate or Stop buttons. When the user clicks the Calculate button, the answer should be calculated. When the user clicks the Stop button, the program should stop running. [End of Task] Arrays Arrays are very powerful to use in LabVIEW. In all your applications you would probably use both onedimensional arrays and two-dimensional arrays. Task 4: Arrays Create the following program:

9 9 Virtual Instruments with LabVIEW [End of Task] SubVIs Creating and using SubVIs are very important in LabVIEW. A SubVI is like a function or subroutine in other languages. Here we will learn to create and use existing SubVIs. Task 5: SubVIs Step 1: Create a SubVI from the simple Calculator created in a previous task. You have to create an Icon for you SubVI using the Icon Editor:

10 10 Virtual Instruments with LabVIEW You also need to create input/output Connectors Step 2: Create a new program that uses the SubVI, like this: [End of Task] Plotting Data LabVIEW have powerful features for plotting different kind of data. Below we see the Graph palette in LabVIEW.

11 11 Virtual Instruments with LabVIEW Task 6: Plotting Create the following program: You may want to use the following function in order to create some random data: Create a Chart and use it inside a While Loop. [End of Task] Virtual Instruments Now you have learned the basic features in LabVIEW and you are ready to create your own Virtual Instruments. Task 7: Virtual Instruments

12 12 Virtual Instruments with LabVIEW In this task you will need everything you have learned so far (and probably a little more). Create a Virtual Instrument with the following components: 1. Toolbar 2. Owned Label 3. Numeric Control 4. Free Label 5. Numeric Control Terminal 6. Knob Terminal 7. Numeric Constant 8. Multiply Function 9. Icon 10. Knob Control 11. Plot Legend 12. XY Graph 13. Wire Data Path 14. XY Graph Terminal 15. Bundle Function 16. SubVI 17. For Loop Structure Below we see the front panel and the block diagram for the virtual instrument.

13 13 Virtual Instruments with LabVIEW The SubVI (number 16) could be reading the temperature from a temperature sensor using a DAQ (Data Acquisition) device, but in our case we will just create a simple simulator using, e.g. the built-in Random Number VI to create random temperature values. We will learn more about acquiring data from DAQ devices later.

14 Telemark University College Faculty of Technology Kjølnes Ring 56 N-3914 Porsgrunn, Norway Hans-Petter Halvorsen, M.Sc. Telemark University College Department of Electrical Engineering, Information Technology and Cybernetics Phone: Blog: Room: B-237a Faculty of Technology, Postboks 203, Kjølnes ring 56, N-3901 Porsgrunn, Norway. Tel: Fax: