Creating Order Plots Using The DATS Rotating Machinery Software

In this tutorial we will be creating order plots using waterfall and intensity displays using use the DATS.toolbox and Rotating Machinery Analysis option.

To begin, a noise, vibration or other signal of interest should be captured along with a tachometer signal.

In Figure 1 we have loaded a time series (in this case an acceleration signal) and a time series of a tachometer pulse train into the DATS software.

What is waterfall frequency spacing? And how does the DATS parameter ‘Requested Frequency Spacing’ work?

Let us try to understand what waterfall frequency spacing is. Waterfall frequency spacing is the gap between spectral lines in an FFT plot.

For example, if you had an analysis frequency of 0Hz to 100Hz and 100 spectral lines, then Frequency Spacing is 1Hz.

So why is there a ‘Requested Frequency Spacing’ and an ‘Actual Frequency Spacing’? Continue reading What is waterfall frequency spacing? And how does the DATS parameter ‘Requested Frequency Spacing’ work?

What is “waterfall smearing”?

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. Continue reading What is “waterfall smearing”?

How Do I Get An XYZ Resultant Waterfall

A user has three signals captured using a triaxial accelerometer and asked “What is the simplest way to get the XYZ resultant from run-up file?” He had tried forming a resultant of the raw time histories, but didn’t fully understand the resultant time history.

Of course, the correct way of processing the data is to calculate the individual waterfalls from the x, y & z data and then calculate a resultant waterfall. Continue reading How Do I Get An XYZ Resultant Waterfall

How Do I Get Articulation Index (AI) vs. Speed?

Use the following sequence to get the Articulation Index (AI) vs rotational speed:

1. Perform waterfall analysis on your noise signal (+ tacho). This gives you a standard waterfall display
2. On the waterfall result perform the analysis
Analysis->Noise, Vibration and Harshness->Spectrum Input->Sound Quality Auto Extract
Number of Cylinders = x  (set to appropriate value)
Write metrics to Input dataset = True
Set required metric to True

In this case select either \$AI_ANSI or \$AI_VEH.
These are different calculations with
AI_ANSI is calculated in the range 0 to 1
AI_VEH is calculated as percentage in range 0 to 100