Exhaust Vibration Measurement - Customer Requirement One of Prosig's customers needed to perform exhaust vibration measurement on some of their vehicles. They contracted Prosig to take the measurements and provide reports of the…
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.
The maximum analysis frequency is always half the sample rate of the input signal.
So if your data is captured at 50kHz the maximum analysis frequency will be 25kHz.
The RMS of a time history is a measure of the signal's overall energy and is often used when extracting features from a signal for prognosis and trending of vibration…
When analysing a waterfall or performing order analysis it is important to consider the frequency resolution or the frequency spacing.
There is often a desire to increase the resolution to finer and finer detail. But that is a process of diminishing returns, and actually fraught with danger. And that danger is waterfall smearing. (more…)
By power spectrum we are talking about an ASD (Auto Spectral Density) or PSD (Power Spectral Density). In fact PSD is often used when really ASD would be more correct.
Taking any signal and performing a frequency analysis using an ASD or a PSD will give the energy over a range of frequencies. (more…)
In our previous post on this subject we briefly looked at how we can use the detailed design information of bearings and gearboxes to look for specific fault conditions by collecting vibration information and analysing their frequency spectra. Amplitude modulation of the vibration signatures is common and we have seen how this causes side-bands to be present in the frequency domain.
Bearings and gearbox vibration are fundamental issues for rotating machines in many industrial applications. These are critical components and, as such, any failure can prove expensive in both repair cost…
An investigation was made of a sample of automotive components where some were exhibiting a high frequency “tick” or rattle during each operating cycle. This feature could be heard above the normal operating noise. The problem this posed was to measure and analyze components in an objective fashion and classify components as “good” or “bad”.
In many instances we need to filter a signal to remove unwanted frequencies. If we use classical filters such as Butterworth, Chebyshev or even Bessel then a phase delay is introduced. This phase delay is itself a function of frequency so that the signal content at one frequency is delayed a different amount to that at another frequency. Why does this matter?