【導(dǎo)讀】openablankVI.diagrammenubar.theblockdiagram.andamplitudeof2.

　　

【正文】 e Instrument I/O Assistant Express VI. 2. Select the Instrument I/O Assistant Express VI on the Input palette and place it on the 14 block diagram. 3. Click the Show Help button, shown at left, in the upper right corner of the Instrument I/O Assistant dialog box. Notice how the Show Help button displays the help to the right of the dialog box. The help window on top contains procedural information about using the Instrument I/O Assistant. The help window below provides contextsensitive help about various controls and indicators in the dialog box. 4. Follow the procedures in the help window on top to select the instrument with which you want to municate. 5. If necessary, configure the properties of the instrument. 6. Click the Hide Help button, shown at left, in the upper right corner of the Instrument I/O Assistant dialog box to minimize the help window. Acquiring and Parsing Information for an Instrument After selecting the instrument, you can send mands to the instrume nt to retrieve data. In this exercise, you will learn to use the Instrument I/O Assistant Express VI to acquire and parse identification information for an instrume nt. Complete the following steps to municate with your instrument. 1. Click the Add Step button, and select Query and Parse. 2. Enter *IDN? in the Enter a mand text box. *IDN? is a query that most instruments recognize. The response is an identification number string that describes the instrument. If the instrument does not accept this mand, refer to the reference manual for the instrument for a list of mands the instrument does understand. 3. Click the Run Sequence button. The Instrument I/O Assistant sends the mand to the instrume nt, and the instrume nt returns its identification information. 4. Parse the instrument name as an ASCII string. You also can use Instrume nt I/O Assistant to parse ASCII numbers and binary data. 15 5. Click the Parsing help button, shown at left, in the Instrument I/O Assistant dialog box for more information about parsing data. 6. Assign a name to the token in the Token name text box. A token is a parsed data selection. 7. Click the OK button to return to the block diagram. Notice that the name that you entered in the Token name text box is the output of the Instrume nt I/O Assistant Express VI, shown at left. Summary The following topics are a summary of the main concepts you learned in this chapter. DAQ Assistant Express VI You can use the DAQ Assistant Express VI to graphically configure channels or mon measurement tasks. Using the DAQ Assistant Express VI, you can interactively build a measurement channel or task. Place the DAQ Assistant Express VI on the block diagram to configure channels and tasks for use with NIDAQmx for data acquisitio is a programming interface for municating with data acquisition devices. You can use the DAQ Assistant Express VI to control devices supported in NIDAQmx. Refer to the Taking an NIDAQmx Measurement in LabVIEW help tutorial for information about the DAQ Assistant. To launch this help tutorial, select Help187。Taking an NIDAQmx Measurement in LabVIEW. Refer to the National Instruments Web site at supported in NIDAQmx. If your device is not supported in NIDAQmx, refer to the LabVIEW Measurements Manual for information on using Traditional NIDAQ for data acquisition. Tasks 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 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 16 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 VI An 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 Instrume nts offers thousands of instrument drivers online. Visit the NI Instrument Driver Network at driver for your instrument. 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 Instrume nt I/O Assistant to municate with a serial, Ether, or GPIB instrument and graphically parse the response. Start the Instrument I/O Assistant by placing the Instrume nt 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.