Arquitecture Data

Acquiring Data
Approximate Time
You can complete this exercise in approximately 15 minutes.

Background
NI-DAQmx is a programming interface you can use to communicate with data acquisition devices. Measurement & Automation Explorer (MAX) is a tool automatically installed with NIDAQmx and used to configure National Instruments hardware and software. This exercise introduces you to the ExpressVIs used to acquire data using NI-DAQmx. With NIDAQmx you can create simulated devices in MAX, so no data acquisition hardware is required to complete this exercise. An NI-DAQmx simulated device is a software replica of data acquisition hardware.

Overview
In the following exercise, you will create an NI-DAQmx task that continuously takes a voltage reading and plots the data on a waveformgraph. You will use the DAQ Assistant Express VI to create the voltage task. The voltage task will acquire data from an NI-DAQmx simulated device that you configure in MAX.

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Completed Exercise

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Step-by-Step Instructions
1. Creating a Simulated DAQ Device
Complete the following steps to configure a simulated data acquisition device in MAX. a. Launch Measurement & Automation Explorer(MAX) by double-clicking the desktop icon or navigation to Programs » National Instruments » Measurement and Automation in the Windows Start menu.

b. Click My System and right-click Devices and Interfaces. c. Select Create New... in the dropdown menu.

d. Select NI-DAQmx Device » NIDAQmx Simulated Device and click Finish. The Choose Device window will prompt you to select a device.

Withthis list, you can browse hundreds of devices supported by NI-DAQmx. You can create an NI-DAQmx simulated device of nearly any NI-DAQmx-supported device.

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e. Select M Series DAQ » NI PCI-6221 and click OK. The NI-DAQmx simulated device will appear in the Configuration pane within MAX.

The icon color of the NI-DAQmx simulated devices differs from real devices. Real devices are green andchassis are grey ; simulated devices and chassis are yellow.

2. Creating an NI-DAQmx Task
In NI-DAQmx, a task is a collection of one or more channels, timing, triggering, and other properties. Conceptually, a task represents a measurement 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 followingsteps to create and configure a task that reads a voltage level from your NI-DAQmx simulated device: a. Open a new VI. b. On the block diagram, display the Functions palette and select Express » Input to display the Input palette. c. Select the DAQ Assistant Express VI on the Input palette and place it on the block diagram. The DAQ Assistant launches and the Create New dialog box appears.

d.Click Analog Input under Acquire Signals. e. Select Voltage to create a new voltage analog input task. The dialog box displays a list of channels for our simulated PCI-6221. The channels listed depends on the number of channels on the selected device.
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f. In the Supported Physical Channels list, select ai0 and click the Finish button. The DAQ Assistant opens a dialog displaying options forconfiguring the selected channel to complete a task.

g. In the Input Range section of the Settings page, enter 10 for the Max value and enter -10 for the Min value.

h. Select N Samples from the Acquistion Mode menu in the Timing Settings section. i. Enter a value of 1000 in the Samples To Read box.

3. Testing the Task
You can test the task to verify that you correctly configured the channel.Complete the following steps to confirm that you are acquiring data: a. Click the Run button once or twice to confirm that you are acquiring data. b. Click the OK button to save the current configuration and close the DAQ Assistant. LabVIEW automatically builds the VI based on this configuration. c. Save the VI as Read Voltage.vi on the desktop.

4. Graphing Data from a DAQ Device
You can...