测控技术及仪器_论文翻译英文

测控技术及仪器_论文翻译英文内容摘要：

duce Samples VI 6. Display the front panel and run the VI. 7. Click the Enable switch. The table displays the mean values of every 25 samples of the sine wave. Notice if the Enable switch is off, the table does not record the mean values. 8. Stop the VI. 9. Experiment with properties of the table by using the Table Properties dialog box. For example, try changing the number of columns to one. 10. Save and close this VI. Summary The following topics are a summary of the main concepts you learned in this chapter. Using the LabVIEW Help Resources You can use the Context Help window and the LabVIEW Help to learn more about Express VIs. Both provide information that describe the functionality of the Express VI and how to configure the Express VI. The following is a summary of the different ways you learned to use the help resources in this chapter. • The Context Help window displays basic information about LabVIEW objects when you move the cursor over each object. Objects with context help information include 8 VIs, structures, palettes, and dialog box ponents. • When you place an Express VI on the block diagram, the Context Help window displays a brief description of the Express VI and information about how you configured the Express VI. • You can find and select an Express VI and other block diagram objects in the LabVIEW Help. Click the Place on the block diagram button to select a block diagram object and place it on the block diagram. • To navigate the LabVIEW Help, use the Contents, Index, and Search tabs. Use the Contents tab to get an overview of the topics and structure of the help. Use the Index tab to find a topic by keyword. Use the Search tab to search the help for a word or phrase. Customizing the Block Diagram Code There are many controls, indicators, Express VIs, and structures that you can use to customize a VI. To customize a VI, you can create controls and indicators, control when a VI stops running, and display generated data in a table. Creating Controls and Indicators Create controls and indicators that are wired to Express VIs from the block diagram by rightclicking the Express VI input, output, or wire, and selecting an option from the Create shortcut menu. Controlling When a VI Stops Running Use the While Loop to continually run the code enclosed within the loop. The While Loop stops running when a stop condition is met. When you place or move an object in a While Loop near the border, the loop automatically resizes to add space for that object. The Execution Control palette includes objects that let you control the number of times a VI runs, as well as the speed at which the VI runs. Displaying Data in a Table The table indicator displays collected data. Use the Build Table Express VI to build a table of collected data. 9 Acquiring Data and Communication with Instruments This chapter introduces you to the Express VIs you use for data acquisition and instrument munication on a PC running Windows. Refer to the LabVIEW Measurements Manual for information about data acquisition and instrument munication on all platforms. Acquiring a Signal In the following exercises, you will use the DAQ Assistant Express VI to create an NIDAQmx task. Refer to the Taking an NIDAQmx Measurement in LabVIEW help tutorial for information about additional methods you can use to create NIDAQmx tasks. To launch this help tutorial, select Help187。 Taking an NIDAQmx Measurement in LabVIEW. Note The following exercises require that you have installed NIDAQmx and an NIDAQmxsupported device. Refer to the National Instruments Web site at DAQmx installed or an NIDAQmxsupported device, refer to the LabVIEW Measurements Manual for information about using Traditional NIDAQ for data acquisitio n. Complete the following exercises to create an NIDAQmx task that continuously takes a voltage reading and plots the data on a waveform graph. You can plete the exercis es in approxim ately 30 minutes. Creating an NIDAQmx Task In 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 ameasurement or generation you want to perform. For example, you can create a task to measure temperature from one or more channels on a DAQ device. Complete the following steps to create and configure a task that reads a voltage level from a DAQ device. 1. Open a new VI. 2. Select the DAQ Assistant Express VI, shown at left, on the Input palette and place it on 10 the block diagram. The DAQ Assistant launches and a Create New dialog box appears. 3. Click the Analog Input button to display the Analog Input options. 4. Select Voltage to create a new voltage analog input dialog box displays a list of channels on each DAQ device installed. The number of channels listed depends on the number of channels you have on the DAQ device. 5. In the My Physical Channels listbox, select the physical channel to which the signal is connected,。