Power Spectral Density (PSD) and Vibration Testing


Power Spectral Density (PSD) is a powerful analysis tool for anyone running random vibration tests. Resonances and harmonics, hidden in a time history graph, become clearly visible in a PSD graph. In practice, generating a PSD is usually the first step in examining and analyzing a random waveform.

The process and calculations for generating a PSD are easily implemented within both the VibrationVIEW and the ObserVIEW software packages. Start with a time history file, enter a few parameters, click on a button, and there it is, a PSD graph.

Except, to create a ‘good’ PSD graph, one that gives accurate insights into a test, it is vital that the engineer using the software understands the underlying PSD concepts. Without that understanding, the PSD parameter choices are unlikely to properly fit the specific test situation and the PSD generated won’t give clear insight into what the Device Under Test is really experiencing.

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

A graphic of overlapping windows for PSD generation

VR wants our customers to be effective, so we now have two types of PSD descriptions in our VRU course, Random Testing. The course begins with lessons that offer a text-based description, enhanced by example graphs, of the multiple steps involved in calculating 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 others that provide 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 take a look and give us your feedback.

Random Vibration Testing Course


June 26, 2019


Thomas Roberts



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