8.4.3. Campbell
A Campbell diagram represents the vibration frequencies of a system at various operating RPMs. A traditional Campbell diagram uses an equation for rotor motion to express the external force caused by the rotational frequency as a periodic function. This function is mapped on a graph, which allows you to analyze the vibration characteristics of a system. A transient Campbell diagram relies on a test or simulation of a complicated rotor system for which an equation of mode cannot be produced. To create such a diagram, you must track the increase in RPM against time and record the system response to each RPM status. Then, you must partition the data and input it into a fast Fourier transform (FFT) algorithm in order to display the frequency response on a 3D graph. If you can implement a steady RPM increase in a rotor system, then you can produce the frequency response characteristics of that system and produce a graphical representation similar to a mathematical Campbell diagram.