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Waterfall and Cascade Plot (Analog Tachometer, DAQmx)

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Overview

This VI demonstrates how to display a waterfall and cascade plot. Waterfall and cascade plots are types of spectral maps. A spectral map is a three-dimensional display of a noise or vibration spectrum as a function of time or speed. The spectrum can be a frequency or order spectrum. A spectral map provides an excellent overview of the frequency or order content of a signal related to the incremental time or speed. A spectral map can help you locate strong noise or vibration components, identify the components changing with the rotational speed, and the fixed components within a certain frequency range. Because a spectral map provides overall signal information, it is usually performed as the first step in order analysis applications. You can locate the signal components of interest from the view of time, speed, frequency, or order. After you locate the components of interest, you can perform some more detailed analysis with other functions such as order power spectrum, order magnitude and phase, or order waveform.

Use a waterfall plot to observe frequency or order spectrum changes versus time. A waterfall plot consists of a series of spectra acquired at consecutive times. The abscissa displays frequency or order. The ordinate axis shows the time. The third axis is the amplitude or power. A waterfall plot is used primarily for online analysis, because it shows how vibration changes with time and indicates which components are related to rotational speed.

Use a cascade plot to observe frequency or order changes versus rotational speed. A cascade plot consists of a series of spectra acquired at consecutive speeds, either increasing or decreasing. The abscissa displays frequency or order. The ordinate axis shows speed and the third axis is the amplitude or power. You can use a cascade plot for both online or offline analysis. A cascade plot is used primarily to show results for tests such as run-up and coast-down tests. The components that move across the plot as the speed changes are the order components, while fixed frequency components move straight up the plot. You can use this cascade plot feature to recognize machine resonances which occur at fixed frequencies.

This VI uses DAQmx VIs to acquire sound or vibration signals and an analog tachometer signal and displays the waterfall and cascade plots continuously. The cascade plot can only be displayed for a run-up or coast-down test. This program is a shipping example VI included with the NI Sound and Vibration Measurement Suite and NI Sound and Vibration Toolkit.

This Virtual Instrument is designed to work with data acquisition hardware from National Instruments. To find compatible hardware for this application, visit ni.com/soundandvibration.

This software is written in LabVIEW, a graphical programming language designed for scientists and engineers. For more information about LabVIEW, visit ni.com/labview.

Sound and Vibration Developers Library
The NI Sound and Vibration Developers Library is your one-stop online resource for learning about and downloading code for acoustic analysis, machine diagnostics and audio test functions. On this page, you will find links to detailed tutorials, application notes, example programs, and analysis function descriptions.

More information on National Instruments signal processing can be found at the Signal Processing Resource Center.

Downloads

Filename: waterfall_and_cascade.vi
Requirements: View

Front Panel


This is a picture of the VI's front panel. To view the block diagram and additional documentation, download the attached file.

This example requires LabVIEW and the Sound and Vibration Measurement Suite.  If you do not have access to these, you can always try them out online at the LabVIEW Online Evaluation.


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Requirements


Filename: waterfall_and_cascade.vi

Software Requirements


Application Software: LabVIEW Full Development System 8.2
Toolkits and Add-Ons: LabVIEW Sound and Vibration Toolset 5.0
Language(s): LabVIEW

Hardware Requirements


Hardware Group: Multifunction DAQ (MIO), Dynamic Signal Analyzers (DSA)
Hardware Model: NI 9205, NI 9205 D-Sub, NI 9206, NI 9215, NI 9215 BNC, NI 9221, NI 9221 D-Sub, NI 9225, NI 9239, PCI-4461, PCI-4462, PCI-4472, PCI-4472B, PCI-4474, PCI-6010, PCI-6013, PCI-6014, PCI-6023E, PCI-6024E, PCI-6025E, PCI-6031E, PCI-6032E, PCI-6052E, PCI-6053E, PCI-6071E, PCI-6220, PCI-6221, PCI-6221 (37-Pin), PCI-6222, PCI-6224, PCI-6225, PCI-6229, PCI-6230, PCI-6232, PCI-6233, PCI-6236, PCI-6238, PCI-6239, PCI-6250, PCI-6251, PCI-6254, PCI-6255, PCI-6259, PCI-6280, PCI-6281, PCI-6284, PCI-6289, PXI-6035E, PXI-6052E, PXI-6053E, PXI-6071E, PXI-6220, PXI-6221, PXI-6222, PXI-6224, PXI-6229, PXI-6230, PXI-6232, PXI-6233, PXI-6236, PXI-6238, PXI-6239, PXI-6250, PXI-6251, PXI-6254, PXI-6255, PXI-6259, USB-6019, USB-6210, USB-6220, USB-6220 Mass Term, USB-6221, USB-6221 BNC, USB-6229 Mass Term, USB-6251 BNC
Driver: NI-DAQmx 8.3

 
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This example program (this "program") was developed by a National Instruments ("NI") Applications Engineer. Although technical support of this program may be made available by National Instruments, this program may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this program with each new revision of related products and drivers. THIS EXAMPLE PROGRAM IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).