Online LabVIEW Evaluation: Exercise 2

• Open a blank VI by clicking File > New VI

First, we will use an Express function to acquire measurements from the preconfigured simulated DAQ.

• Right click on the Block Diagram, navigate to Express >> Input >> DAQ Assistant
• A DAQ Assistant dialog will appear. Select Acquire Signals >> Analog Input >> Acceleration -> IEPE and press Next.
• We have preconfigured the environment to simulate a connection with an NI 9234 module, which contains 4 channels of Accelerometer inputs. Hold Shift Key and select the first two channels, ai0 and ai1 and click Finish.
• We would like the program to continuously acquire a signal until we stop it, so change the Acquisition Mode to Continuous Samples.



Before clicking OK, you can quickly test this out by clicking Run in the DAQ Assistant. The simulated channels are configured to simulate a sine wave. Once you're done, you can press Stop and then OK.



• Because you selected Continuous Samples LabVIEW will prompt you to allow it to automatically create a loop around the DAQ Assistant Function. Click on Yes.

You now have a program that is acquiring measurements from two channels of a simulated DAQ device. To display this data on the user interface, let's add a chart.

• Right-click on the Front Panel, navigate to Graph and select Waveform Chart
• On the Block Diagram, place the chart indicator inside the loop, and connect a wire from the data output node of the DAQ Assistant to the input node of the chart.
• On the Front Panel, change the label of the chart to Accelerometer Data, and expand the plot legend to show both channels



Now you can run and watch the chart display the acquired data from our simulated DAQ device.

Let's go a step further and explore how we could analyze this data as we acquire it. In this case, let;s say we'd like to perform a Power Spectrum analysis of the signal we are acquiring.

• Right click on block diagram and navigate to Express >> Signal Analysis >> Spectral Measurement and place the function inside the While Loop.
• Select Power Spectrum and select Linear result. Press OK.
• Connect a wire from DAQ Assistant Data output node to Spectral Measurement Signals input node
• To display this on the User Interface, right-click on the Front Panel, navigate to Graph and select Waveform Graph. Change the label of the graph to Power Sepctrum Data. Change the label of the x-axis from Time to Frequency (Hz).
• Right-click the Waveform Graph and select Properties. In the Scales tab, for the x-axis, uncheck the Autoscale box and change the Maximum to 20.
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• On the block diagram, connect a wire from Spectral Measurement's Power Spectrum output node to Power Spectrum Data input node.



Your program is now ready to run!

• Click on the Run Button on the Front Panel toolbar
• Watch as the program acquires data from the DAQ device and displays it. The program also analyzes the data and displays the calculated Power Spectrum. 
• Once you are done, press on the Stop Button. This will end the program