Understanding Interactive FFT

This article outlines what Interactive FFT is, how it helps you, how you can use it, and how you can access it.

What is Interactive FFT?

Interactive FFT is a feature that displays the Fourier transform of the vibration signal collected by FitMachines, which can be used for traditional fault diagnostics. 'FFT' is an acronym of the Fast Fourier Transform algorithm.

This is different from the data displayed on the AI Output chart as AI Output displays a compressed summary of the vibration data, for the purpose of detecting unusual behaviour.

This feature provides you with an Interactive FFT every 2 days.  

Interactive FFT Still

Why is it useful?

This chart can assist with preliminary fault identification, and help to determine which maintenance activities are likely to resolve the issue.

How do I use it?

As the name gives away, the FFT chart is interactive. That means you can:

  • Zoom in and out to analyse a portion of a spectrum
  • Show or delete annotations
  • Show harmonic markers

Zooming In

To analyse a portion of a spectrum you can zoom in using the slider at the bottom of the chart, or use a bounding box.

Zooming In Using the Slider:

To adjust the frequency you are viewing, simply click and drag the highlighted section of the slider. To zoom in and see a smaller range, adjust by dragging the edges.

To autoscale the vertical axis within the horizontal range, and ensure the range you are viewing is scaled to fit the chart, check the 'Autoscale within Horizontal Range' box at the bottom of your screen (see example gif below). 

AutoscaleWithinRange

 

Zooming In Using a Bounding Box:

Alternatively, you can zoom in vertically using a bounding box. To do this, draw a rectangle over the desired range of the chart. This will automatically zoom you in and autoscale the range to fit the chart (see example gif below).

VerticalRegionZoom

Show or Delete Annotations

You can annotate the chart by clicking the peaks. This will add the exact details of the peak to the chart (in the format Frequency, Acceleration) so you can easily compare them side-by-side. 

The feature will not work unless the 'Show Point Annotations on Click' checkbox is selected at the bottom of your screen. However, this should be selected automatically.

To clear the chart of any annotations, click the 'Delete all Click Annotations' button (see example gif below).

AnnotationOnClick

Show Harmonic Markers

You can choose to show harmonic markers at either a specified frequency or aligned with the peaks.

Harmonic markers highlight which parts of the spectrum are caused by vibration with a particular fundamental frequency. For example, if you have a vibration that repeats at 50Hz, if it isn't a sinusoid, then an FFT of it will have peaks at 50, 100, 150, 200, and so forth. 

On the chart, these repetitions are shown as 1x, 2x, 3x, 4x, and so forth, where 1x represents the fundamental frequency. 

Showing Harmonic Markers at a Specified Frequency:

To manually place markers at a specified frequency, check the 'Show Harmonic Markers' box, and type or use the arrows to change the frequency (see example gif below).

ManualHarmonicPositioning

Automatic Harmonic Marker Placement

Alternatively, you can automatically place the markers aligned with the peaks through peak pair selection. This is done by clicking the 'Align Harmonic Markers From Peak Pair' button, and selecting two peaks (see example gif below). 

HarmonicMarkerPlacement

How can I access it?

On FitMachine V3s, higher-resolution FFT data is transmitted on a regular basis to facilitate more advanced vibration analysis. The most recent such FFT can be viewed by visiting a specific FitMachine's MachineCloud page and clicking the "Latest FFT" button.

Interactive FFT

Please note that the capacity for Interactive FFT is currently only available for V3 FitMachines at no cost for a limited time and requires activation for your organisation on our behalf. Once activated, the chart will be located on the device page for any asset.

If you're interested in activating this feature for your assets or have any questions, please contact MOVUS Support here or message us by clicking the chat box at the lower right-hand corner of your screen.