【正文】 注意，如果 Enable 開(kāi)關(guān)關(guān)閉，表格不再記錄平均值。程序框圖顯示如圖 34 所示。稱為選取框(marquee)的移動(dòng)虛線邊框突出 Build Table Express VI、Table 連線終端和連接它們的連線。2. 顯示程序框圖。注意，如果 Enable 開(kāi)關(guān)處處于打開(kāi)狀態(tài)，波形圖顯示變慢的信號(hào)；如果 Enable 開(kāi)關(guān)處于關(guān)閉狀態(tài)，波形圖將不顯示變慢的信號(hào)。3. 關(guān)閉 Configure Time Delay 對(duì)話框。1．在程序框圖中，從 Execution Control 選板中選擇 Time Delay Express VI，把它放置在循環(huán)內(nèi)。注意，VI 一直運(yùn)行，直到您點(diǎn)擊 STOP 按鈕。4. 點(diǎn)擊并對(duì)角拖拉，使之包括所有的 Express VIs 和連線，如圖 33 所示。1．顯示前面板，運(yùn)行 VI。 注意，您添加的控制件和顯示件自動(dòng)在前面板上顯示，且有與它們的功能對(duì)應(yīng)的標(biāo)注。注意，合并信號(hào)函數(shù)(Merge Signal Function)出現(xiàn)。4. 右擊 Simulate Signal Express VI 的 Sine 輸出和 Signal Compression Express VI 的Signals 輸入之間的連線，單擊 CreateGraph Indicator。完成下面的步驟在程序框圖中創(chuàng)建控制件和顯示件。8. 關(guān)閉 Configure Sample Compression 對(duì)話框。5. 移動(dòng)光標(biāo)到程序框圖。2. 點(diǎn)擊 Search 標(biāo)簽，在 Type in the word(s) to search for 文本框內(nèi)鍵入 sample pression。10. 保存此 VI 到容易找到的位置，命名為 Reduce 。7. 注意 Result Preview 窗口內(nèi)顯示的信號(hào)，自動(dòng)改變來(lái)反映您配置的正弦波。3. 通過(guò) Context Help 窗口提供的信息，找到可以輸出一個(gè)正弦波信號(hào)的 Express VI。1. 如果 Context Help 窗口沒(méi)有出現(xiàn)，可以按 CtrlH 鍵打開(kāi)它。2. 如果 Functions 選板不可見(jiàn)，在程序框圖內(nèi)的任何空白區(qū)右擊，即會(huì)跳出 Functions 選板。完成下面的步驟來(lái)打開(kāi)一個(gè)空 VI。新的 VI 程序?qū)崿F(xiàn)產(chǎn)生信號(hào)、減少信號(hào)的采樣點(diǎn)，并在前面板的表格中顯示最終數(shù)據(jù)。Taking an NIDAQmx Measurement in LabVIEW.Refer to the National Instruments Web site at , refer to the LabVIEW Measurements Manual for information on using Traditional NIDAQ for data acquisition.TasksIn NIDAQmx, a task is a collection of one or more channels, timing, triggering, and other properties that apply to the task itself. Conceptually, a task represents a measurement or generation you want to perform.For example, you can configure a collection of channels for analog input operations. After you create a task, you do not have to configure the channels individually to perform analog input operations but instead access the single task. After you create a task, you can add or remove channels from that task.Refer to the Channels Versus Tasks section of Chapter 5, Creating a Typical Measurement Application, of the LabVIEW Measurements Manual for more information on channels and tasks.Instrument I/O Assistant Express VIAn instrument driver is a set of software routines that control a programmable instrument. Each routine corresponds to a programmatic operation such as configuring, reading from, writing to, and triggering the instrument. National Instruments offers thousands of instrument drivers online. Visit the NI Instrument Driver Network at If a driver is not available for your instrument, you can use the Instrument I/O Assistant Express VI to municate with your instrument. You can use the Instrument I/O Assistant to municate with a serial, Ethernet, or GPIB instrument and graphically parse the response. Start the Instrument I/O Assistant by placing the Instrument I/O Assistant Express VI on the block diagram or by doubleclicking the Instrument I/O Assistant Express VI icon on the block diagram.Refer to the Instrument I/O Assistant Help for information about municating with an external device. 出 版 社：National Instruments起 止 頁(yè)：31—47出版日期：2003年4月擴(kuò)展 VI 的特性您可以選擇多個(gè) LabVIEW VI模板中的一個(gè)來(lái)創(chuàng)建您的 VI。Control to create the Enable switch.4. Rightclick the wire linking the Sine output in the Simulate Signal Express VI to the Signals input in the Signal Compression Express VI and select Create187。New VI from the front panel or block diagram menu bar.2. If the Functions palette is not visible, rightclick 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 rightclick 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 SignalComplete 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 CtrlH 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 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 and amplitude of 2.7. Notice how the signal displayed in the Result Preview window changes to reflect the configured sine wave.8. Close the Configure Simulate Signal dialog box.9. Move the cursor over the Simulate Signal Express VI and read the information that appears in the Context Help that the Context Help window now displays the configuration of the Simulate Signal Express VI.10. Save this VI as Reduce to an easily accessible location.Modifying the SignalComplete the following steps to use the LabVIEW Help to search for the Express VI that reduces the number of samples in a signal.1. Select Help187。VI, Function, amp。Graph Indicator.Notice that you can create controls and indicators from the block diagram. When you reate controls and indicators using this method, LabVIEW automatically creates terminals that are labeled and formatted correctly.5. Using the Wiring tool, wire the Mean output in the Sample Compression Express VI to the Sine terminal. Notice that the Merge Signals function appears.6. Arrange the objects on the block diagram so that they appear similar to Figure 32.Tip You can rightclick any w