Prosig Noise & Vibration Measurement Blog » Hanning

Amplitude And Energy Correction – A Brief Summary

John Mathey — Tue, 01 Sep 2009 10:44:01 +0000

Amplitude and energy correction has been and is a continuing point of confusion for many people calculating spectra from time domain signals using Fourier transform methods. The first thing to say, the information contained in data presented as amplitude and energy corrected spectra is equivalent. The only difference is the scaling of the numbers calculated.

Amplitude [...]

Data Windows : What, why and when?

John Mathey — Mon, 20 Jul 2009 08:23:53 +0000

Before we discuss the use of data windows, we should first remind ourselves of three basic properties of the FFT (Fast Fourier Transform) process.

First, energy information in signal must be preserved during transformation. That is, the energy measured on time signal must equal the energy measured on the frequency representation of that signal. Second, an FFT converts [...]

Orders v Time – Comparing Overall Levels

Dr Colin Mercer — Tue, 23 Oct 2007 13:33:06 +0000

By combining a speed signal with a data signal and using the Short Time FFT algorithm (Hopping FFT), it is possible to extract order data directly as a function of time (Orders from Hopping FFT) rather than as a function of speed (Waterfall). This is very useful when analyzing a complete operational cycle which includes run [...]

Average Waterfalls Or Average Orders?

Dr Colin Mercer — Tue, 14 Jun 2005 20:51:52 +0000

One would expect that averaging waterfalls and then extracting orders would give the same result as extracting orders from individual waterfalls and then averaging them. This [...]