Processing pump data – a classic case of amplitude modulation

When dealing with some vibration data from a pump, we observed some strange phenomena in the data. It turned out to be a classic case of amplitude modulation. Here we explain what that means.

Creating An End of Line Vibration Test System

Prosig was contracted by Imperial Electric in Akron, Ohio to integrate a system for end of line vibration test for electric motors they manufacture. The requirement was to qualify motors under…

How do we design or modify a system to avoid resonance?

After finding the natural frequency of a system, what could be done to stop or reduce the systems resonance being excited? Basically put, how do we avoid resonance This is…

Relative signal levels of a sinusoid with and without background noise

In the process of looking at some order data, a question about the accuracy of the measurement of the signal level of discrete frequency signals which were close to the general noise level.  To answer this question, a small DATS worksheet was created which generated 2 signals.  The first signal was a 35 Hz sinusoid which, by itself the spectrum level was measured to be approximately -9 dB (ref 1 V) as seen in Figure 1.

What is the difference between Operating Deflection Shapes (ODS) and Operational Modal Analysis (OMA)?

ODS = Motion of structure vibrating naturally (for example bridge vibration) or when excited by an unknown force (for example generator vibration). Prosig’s Structural Animation software performs ODS analysis.

OMA = Modal Analysis
Prosig’s Modal Analysis software performs OMA. (more…)

Waterfall Analysis: Frequency Resolution and Smearing

When measuring noise and vibration in rotating machines, especially complex devices like automobile engines, it is very important to fully understand what is being measured and what analyses need to…

Removing A-Weighting From Time History Signals

It sometimes occurs that signals are captured with A-weighting applied to the data by the acquisition device. This can be a problem if, for example, you wish to use the data in a hearing test or to use it for a structural vibration analysis. Now, A-weighting allegedly mimics what the ear does to a signal. If we play back an A weighted sound then we perceive a double A-weighted signal which is clearly not intended. When doing structural work it is usually the lower frequencies, say 2kHz or less, that is generally required. A-weighting seriously attenuates the low frequencies and also applies gain above 1kHz.

The Intelligent Way To Sort, Extract & Analyze Signals

This note is based on a real requirement presented to Prosig by a prospective user. It’s the sort of challenge that we relish. This case is a great example of a real-world signal processing requirement and also great test of some of the unique features of Prosig’s DATS software. It also shows the power and flexibility of the new DATS V7.0 worksheets.

Figure 4: Energy corrected spectrum

Amplitude And Energy Correction – A Brief Summary

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.

Acceleration, Velocity & Displacement Spectra – Omega Arithmetic

Accelerometers are robust, simple to use and readily available transducers. Measuring velocity and displacement directly is not simple. In a laboratory test rig we could use one of the modern potentiometer or LVDT transducers to measure absolute displacement directly as static reference points are available. But on a moving vehicle this is not possible.