Exercise 19
Advanced Functions

Several advanced functions of G can be found in the Application Control menu of the Functions Palette. One useful function is called a Property Node. A Property Node can get (Read) and/or set (Write) a property of a VI. For example, a Property Node can be used to close the front panel of a VI when execution is finished. In this exercise you will use this property to create a VI that performs a Fowler-Nordheim analysis using VIs you created in previous exercises.

I.    Examine a Property Node

A VI can be operated under program control (programmatically) when a Property Node is combined with a function that determines the path to the current VI and a function that opens a VI Reference. A property of the VI must be selected from its pop-up menu and the Property Node must be configured to either read (default) or write that property. When a Property Node is placed in a diagram no property is selected.  See Figure 1.

Figure 1. A Property Node Application

If Front Panel –> Open is selected from the Properties pop-up menu the front panel will open (or close) provided a Boolean True (or False) is wired to the Property Node.

II.    Create a VI

Open the software folder. Double click GTsoftware.llb. Select the VI labeled exercise19.vi from the list of VIs in the library and click OK.

Several controls and indicators and a Property Node application were placed on the front panel. Do not change the default values of the controls or the indicator. The Property Node function was configured to keep the front panel open.

Create a VI to perform a Fowler-Nordheim analysis from I-V data in a spreadsheet file. Use the VIs you created in Exercises 14-18. See Figure 2.

Figure 2. Create a VI

The Unbundle function (Cluster menu of the Functions Palette) separates the items in the cluster (in order) as a slope, m, and an intercept, b. Be sure you understand why there is a conversion at the inputs of the VI you create in Exercise 17 (FN Plot.vi).

III.    Add Accouterments to the VI

Add a custom icon to your VI. See Figure 2.

Figure 3. Add Accouterments

IV.    Examine the VI Properties

Open VI Properties... Browse through the menu options to examine the VI properties that have been selected. When you are finished click the button labeled OK.

V.    Run the VI

Open the CEsoftware folder. Double click CEsoftware.llb. Select Export FEEM Data from the Options menu and then select Quit. A file called FEEM.txt will be placed in the software folder.

Run the VI. Navigate to the FEEM Data file (FEEM.txt) in the software folder. Animate the diagram to see how the VI functions.

If the VI is working properly a One Button Dialog box will display the electric field at the tip apex, the corresponding emission area and the tip radius.

Figure 4. Run the VI

Extra Credit

Open the CEsoftware folder. Double click CEsoftware.llb. Select Analyze I-V Data from the Options menu and open FEEM.txt. Your VI mimics the operation of this VI. For extra credit make your VI look and behave like Analyze I-V Data.

VI.    Finish up

Save exercise19.vi as FN Analysis.vi in your GTutorial folder.

Quit LabVIEW.

Congratulations! You have completed GTutorial.