Chem 8153 February 2009 1 Laboratory 3 Virtual Instruments: LabVIEW The objectives of this laboratory session are: (1) Understand the principles behind graphic programming. (2) Understand how a VI that ‘acquires temperature data’ works. (3) Use LabVIEW as a virtual function generator and as a virtual oscilloscope. Introduction LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a graphical programming tool that uses icons instead of textual language to describe the various steps in a program. In academic environments requiring new instrumentation design, this is the most currently used approach to control instruments and acquire data. These two applications of LabVIEW will be put to practice later in the semester. In laboratory this session, we will investigate the tutorial found in LabVIEW, version 6. Prelab Prior to this lab session, confirm that you have access to LabVIEW, version 6. You may use those computers found in our course laboratory room or at the Microcomputer Lab (Smith 101 D). Components and Equipment Needed 1. LabVIEW, version 6 A. Understand the basic concepts in LabVIEW LabVIEW is a complex software package and one can get easily lost. While observing this tutorial or using LabVIEW, take notes. Make sure that your write down where you found the information. It may be difficult to find the information again, when you need it. Introduction. This part of this laboratory experience is mainly focused on getting comfortable with the terminology and concepts of LabVIEW. You will review several definitions, get familiar with virtual instruments (VI’s) and how they work. 1. LabVIEW tutorial. After opening LabVIEW, select “LabVIEW tutorial”. In the newly opened window, read carefully the contents of the following topics: a. What is Labview? b. The Computer is the Instrument c. Virtual Instruments, including Front Panel, Block Diagram, and Icon and Connector d. SubVIs e. The LabVIEW Environment f. Navigating and Searching the Palettes g. Dataflow: The Basic Concept Behind LabVIEWChem 8153 February 2009 2 2. Learning LabVIEW with activities. This is one of the topics also found under “LabVIEW tutorial”. This topic follows the last topic in Part 1, “Dataflow” The Basic Concept Behind LABVIEW’. When you select this topic, the window will display 12 activities with their respective objectives. Do the following activities: a. Open and Run a VI (Topic # 1) b. Use LabVIEW Help Utilities (Topic # 2) c. Create a VI (Topic # 3) d. Document a VI (Topic # 4) e. Debug a VI (Topic # 5) f. Create a Multiplot Chart and Customize your Trends (Topic # 7) g. Save Data to a Spreadsheet File ((Topic # 8) 3. Function generation. You need to carry out Activity # 11, under “Learning LabVIEW with activities”. This activity is called, “Build a Function Generator Using Waveform Data”. After you build your function generator. Save your files. You will need that for your report and for Part B of this laboratory. 4. Graph temperature as a function of time. You need to open Activity # 6, under “Learning LabVIEW with activities”. Select under “Graphs and Charts”, the activity called “Graph Temperature”. This example simulates acquiring data, one value at a time, from a plug-in data acquisition board. Run the VI (click on the White Arrow). Observe how the output changes as the number of measurements and the delay are changed in the front panel. Observe the processing of information by your VI using “Highlight Execution” option (lightbulb in the menu bar of the diagram window). Report. In your report include a printout of both the front panel and the diagram of (i) your function generator and (ii) the Graph Temperature VI. Provide a screen shot of the output of both of these VI’s. Explain succinctly the role of each component in the diagram of each VI. These must be very short explanations. B. Using LabVIEW to create a virtual function generator and oscilloscope. Introduction. You will use the Function Generation VI that you created in Part A to represent the voltage source in the circuit below. You will modify your VI to also plot the VBC (voltage across the capacitor) as a function of time. In other words, you want to use LabView as an oscilloscope measuring VBC. Procedure. a. Open your VI and save a copy under a different name. b. Modify the output of the function generator so that it is processed by the equivalent mathematical representation of a capacitor found in the circuit. Use of the Function Palette is recommended.Chem 8153 February 2009 3 c. Connect the output of the mathematical calculation to a new output. The new output must generate a new trace in the front panel display. d. By changing the frequency, confirm the results that you already obtained in Lab #2 for this circuit. It is recommended to use both a sinusoidal and a square wave. 3 k!A BC˜ 6 !F30 V Report. In your report include a printout of both the front panel and the diagram of (i) your modified VI. Provide a screen shot of the output of both your new VI. Explain succinctly the role of the new components in the diagram. These must be very short explanations. Discuss similarities and differences in the output predicted by your VI and your calculations in the Experiment # 2. Useful Hints for LabVIEW. a. Keep the Context Help turned on. This is found under the Help Menu of each window. It will explain the use and function of each component as the cursor is moved over such component. b. In order to run a VI, you need to click the White Arrow in the bar menu of such VI. c. In order to observe a diagram in action, turn on the Highlight Execution (light bulb) in the menu bar of the diagram window. This will slow down the operation. Do not forget to turn off this option when finished. d. Use the right click mouse to display options associated with a given component in the front panel or