15A.9 Waterfall Display

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This Appendix discusses using the Waterfall Display VIs located on the Waterfall Display palette.

15A.9.1 Using the Display VIs

Waterfall display is a visualization technique that permits the visual representation of various analyses of

nonstationary signals, such as machine run-up, coast down, transients, and others.

Use the Waterfall Display VIs to display FFT spectra from frequency analysis or transient analysis and

octave spectra from octave analysis in waterfall graphs. Refer to Front Panel Displays in the LabVIEW Help

for more information about displaying octave results.

Specific Waterfall Display VIs display the results of frequency analysis and octave analysis in a waterfall

graph. The waterfall display opens in an external window called the Waterfall window.

FIGURE 15A.49 Half-sine pulse SRS (Maximax).

FIGURE 15A.50 Using the SVT shock response spectrum VI.

Virtual Instrumentation for Data Acquisition, Analysis, and Presentation 15-103

© 2005 by Taylor & Francis Group, LLC

Complete the following basic steps to display

results on a waterfall graph:

1. Initialize the display.

2. Send data to the display.

3. Close the waterfall display.

Figure 15A.52 shows the Waterfall window.

15A.9.1.1 Initializing the Display

Use the SVL Initialize Waterfall Display VI to

create a reference to a waterfall display. If you are

displaying octave spectra, use the SVT Initialize

Waterfall Display for Octave VI. Both of the

initializing VIs also enable one to define graph

properties, including the window title, the bounds

of the external window, and the colors used in the

waterfall display.

15A.9.1.2 Sending Data to the Display

The Waterfall window does not open until it

receives data sent to it. Use the SVL Send Data to

Waterfall VI to send data to a waterfall display. Use

the SVT Send Data to Waterfall for Octave VI to

send octave data to a waterfall display.

The SVL Send Data to Waterfall VI is polymorphic

and accepts an array of spectra, such as

that returned by a power spectrum, a twodimensional

(2D) array, or a STFT.

15A.9.1.3 Waterfall Display for Frequency

Analysis

The following example shows how to accumulate

20 spectra and display them in a waterfall graph.

Figure 15A.53 shows the block diagram for the VI.

Twenty data blocks of 1024 samples are acquired. The power spectrum is computed on each block. The

autoindexing capability of the For Loop is used to build an array of 20 spectra. The array or spectra is sent

to the waterfall display. Refer to the LabVIEW Help for information about autoindexing.

15A.9.1.4 Waterfall Display for Transient Analysis

This example illustrates how to use the waterfall display in conjunction with the Transient Analysis VIs.

Figure 15A.54 shows the block diagram for the example VI.

FIGURE 15A.51 Acquired SRS (Maximax).

FIGURE 15A.52 Waterfall display for frequency

analysis.

FIGURE 15A.53 Waterfall display for frequency analysis VI block diagram.

15-104 Vibration and Shock Handbook

© 2005 by Taylor & Francis Group, LLC

The data are scaled and sent to the SVT STFT vs.

Time VI. The SVT STFT vs. Time VI returns a 2D

array. You can use the results in the 2D array in an

intensity graph or connect the 2D array directly to

the SVL Send Data to Waterfall VI. Figure 15A.54

shows the 2D array connected directly to the

Waterfall VI. The while loop keeps the waterfall

display open until the Stop control is set to TRUE.

Note: Connect f 0 and delta f and y 0 and delta y

on the SVL Send Data to Waterfall VI to ensure the

graph shows the proper scales.

Figure 15A.55 shows the result obtained with

the STFT VI illustrated in Figure 15A.54.

15A.9.1.5 Waterfall Display for Octave Spectra

To display octave spectra in a waterfall display, use the SVT Initialize Waterfall Display for Octave and

SVT Send Data to Waterfall for Octave VIs. Figure 15A.56 shows the block diagram for a VI displaying

octave spectra in a waterfall display.

Figure 15A.57 shows the waterfall display created by the VI in Figure 15A.56.

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