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Waterfall and Octave Waterfall Graphs (Sound and Vibration Measurement Suite)

Waterfall displays allow you to represent visually the results of various analyses of nonstationary signals, such as machine or engine run-up, run-down, and transients.

You can use a waterfall graph to display frequency or order spectra from frequency analysis, transient analysis, or order analysis. The following figure shows a sample waterfall graph.

Use a waterfall graph to observe frequency or order spectrum changes versus time. A waterfall graph consists of a series of spectra acquired at consecutive times. The x-axis displays frequency or order. The y-axis displays the amplitude or power. The z-axis displays the time. Use a waterfall graph for both online and offline analysis.

You can change the perspective of a waterfall graph to obtain a cascade plot view. The following figure shows a sample cascade plot.

A cascade plot displays frequency or order changes versus rotational speed. A cascade plot also consists of a series of spectra acquired at consecutive increasing or decreasing speeds. The x-axis displays frequency or order. The y-axis displays the amplitude or power, and the z-axis displays the speed. You can use a cascade plot for both online and offline analysis. You primarily use cascade plots to show results for tests such as run-up and run-down tests.

You can use an octave waterfall graph to display octave spectra from octave analysis. The following figure shows a sample octave waterfall graph.

Use the Waterfall Graph and Octave Waterfall Graph indicators to display waterfall and octave waterfall data. The Waterfall Graph and Octave Waterfall Graph are XControls that include properties you can access manually by right-clicking the graph on the front panel or programmatically by using the Property Node on the block diagram. You can use the properties to set characteristics such as color, perspective, and transparency.

To use the Waterfall Graph and Octave Waterfall Graph, locate the graph on the Sound & Vibration controls palette and place the graph on the front panel window. You then can wire the appropriate output of a VI to the Waterfall Graph or Octave Waterfall Graph on the block diagram.

TipYou can change the perspective of the Waterfall Graph or Octave Waterfall Graph by <Ctrl>-clicking and dragging the display.

You can use the Display VIs to buffer the results of frequency analyses to mimic the behavior of a chart on a Waterfall Graph, to convert a Waterfall Graph to a Colormap, and to convert a Colormap to a Waterfall Graph.

Refer to the following VIs for examples of using the Waterfall Graph or the Octave Waterfall Graph:

  • SVXMPL_Waterfall Display (Simulated) VI: labview\examples\Sound and Vibration\Waterfall Display
  • SVXMPL_Waterfall Display for Octave (DAQmx) VI: labview\examples\Sound and Vibration\Waterfall Display

Displaying Analysis Results with the Waterfall Graph and Octave Waterfall Graph

You can display frequency analysis results in a Waterfall Graph by bundling the data with z-axis information, as shown in the following block diagram.

This example uses the SVFA Power Spectrum VI to perform a frequency analysis of an analog waveform signal. The Bundle function then adds the z-axis information to the data output of the SVFA Power Spectrum VI so the Waterfall Graph can display the individual power spectrum plots along the third dimension.

Some Sound and Vibration VIs, such as the OAT Spectral Map VI, allow you to output data directly to the Waterfall Graph. Place the Waterfall Graph on the front panel window, then select the Waterfall instance of the VI. You then can wire the appropriate output to the Waterfall Graph on the block diagram, as shown in the following block diagram.

You also can display octave analysis results in an Octave Waterfall Graph, as shown in the following block diagram.

This example uses the SVT Third-octave Analysis VI to perform an octave analysis on an analog waveform signal. Similar to the previous example, the Bundle function adds the z-axis information to the data output of the SVT Third-octave Analysis VI so the Octave Waterfall Graph can display the octave analysis plots along the third dimension.


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