音频信号发生器毕业设计论文 翻译 英文--

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Expanding the Features of a VI

You can choose one of many LabVIEW VI templates to use as a starting point. However, sometimes you need to build a VI for which a template is not available. This chapter teaches you how to build and customize a VI without using a template.

Building a VI f rom a Blank Template

In the following exercises, you will open a blank VI and add Express VIs and structures to theblock diagram to build a new VI. You will build a VI that generates a signal, reduces the number of samples in the signal, and displays the resulting data in a table on the front panel. When you complete the exercises, the front panel of the VI will look similar to the front panel in Figure 3-1.

You can complete the exercises in approximately 30 minutes.

F i gure 3-1. Front Panel for the R educe Samples VI

Opening a Blank VI

If no template is available for the task you want to create, you can start with a blank VI and add Express VIs to accomplish the specific task. Complete the following steps to open a blank VI.

1.In the LabVIEW dialog box, click the arrow on the New button and select BlankVI

from the shortcut menu or press the keys to open a blank VI.

Notice that a blank front panel and block diagram appear.

Note You also can open a blank VI by selecting Blank VI from the Create new list in The New dialog box or by selecting File»New VI from the front panel or block diagram menu bar.

2. If the Functions palette is not visible, right-click any blank space on the block diagram

to bring up the temporary version of the Functions palette. Click the thumbtack,

shown at left, in the upper left corner of the Functions palette to

place the palette on the screen.

Note You can right-click on a blank space on the block diagram or the front panel to bring up the Functions or Controls palettes.

Adding an Express VI that Simulates a Signal

Complete the following steps to find the Express VI you want to use and then add it to the block diagram.

1. If the Context Help window is not visible, press the keys to open the

Context Help window. You also can press the Show Context Help Window button, shown at left, to open the Context Help window.

2. Select the Input palette on the Functions palette and move the cursor over the Express

VIs on the Input palette.Notice that the Context Help window displays information about the function of each Express VI.

3. From the information provided in the Context Help window, find theExpress VI that

can output a sine wave signal.

4. Select the Express VI and place it on the block diagram. The Configure Simulate

Signal dialog box appears.

5. Idle the cursor over the various options in the Configure Simulate Signal dialog box,

such as Frequency (Hz), Amplitude, and Samples per second (Hz). Read the information that appears in the Context Help window.

6. Configure the Simulate Signal Express VI to generate a sine wave with a frequency of

10.7 a nd amplitude of 2.

7. Notice how the signal displayed in the Result Preview window changes to reflect the

configured sine wave.