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Power Spectral Density (PSD) and Vibration Testing


Generating a power spectral density (PSD) is often the first step in examining and analyzing a random waveform. A PSD graph displays resonances and harmonics that are not evident in a time-history waveform.

PSD Random Vibration Analysis

Generating a PSD is easy with the VibrationVIEW and the ObserVIEW software packages. Start with a time history file, enter several parameters, and the software takes care of the rest.

Vibration Research software uses Welch’s method for PSD estimation, which applies the fast Fourier transform (FFT) algorithm to the estimation of power spectra.

breakpoint power spectral density

Breakpoint PSD.

Vibration Control

In VibrationVIEW, enter up to 9,999+ frequency or amplitude breakpoints in an easy-to-read format. Use one input channel for control or configure up to 512 channels with multi-channel averaging or notching.

Graphs are easily auto-scaled, and the cursor is adjustable. Data and text annotations can be easily placed on the graphs, and data values update live with changes.

Vibration Analysis

In ObserVIEW, import a file to view, edit, and analyze data. Employ an advanced analysis of one or multiple waveforms with features such as resampling, filtering, advanced data analysis (PSD, transfer function, etc.), and Multimedia Sync.

ObserVIEW PSD Trace

PSD with graph trace.

Understanding PSD Parameters

To create a good PSD graph (one that provides accurate test insights), the engineer must understand the underlying concepts of the PSD. Without such, their parameter choices are not likely suitable, and the PSD will not accurately represent the device under test’s (DUT) response.

For example, windowing and overlapping parameters affect the shape of a PSD, and there are many choices for both. Effective analysis is built on informed parameter choices.

A graphic of overlapping windows for PSD generation

Overlapping windows for PSD generation.

VRU Course: Random Testing

VR is committed to providing our customers with valuable information. Our VRU Random Testing course includes two descriptions of the PSD. It begins with a text-based description and example graphs of the steps to calculate a PSD. Each step is a mathematical process, but these descriptions avoid equations while still communicating the critical concepts.

The initial lessons are followed by a mathematically rigorous description of the PSD and related calculations. However you like to learn, there should be something for you in this course. We hope you’ll look and give us your feedback.

Random Vibration Testing Course


June 26, 2019


Thomas Roberts



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