1
Read the record
Pick a synthetic example or load your own CSV. Enter the sampling rate and unit; the record summary appears at once.
Spectra
Inspect a vibration record with a spectrum, an envelope spectrum and a kurtogram, and mark 1×, 2× and bearing fault frequencies on the chart. The maths runs in your browser; your record is not uploaded.
Spectra in half a minute
A short tour from the waveform to the bearing frequencies, and how to read the results.
Read the transcript
Narrates how a vibration record moves from the waveform and spectrum to the bearing frequencies in the envelope.
Narration: synthetic voice (Piper, voice “Joe”, CC0 public domain). Captions are burned into the video.
In three steps.
2
Split it into frequencies
The waveform, FFT spectrum and spectrogram come together. Running speed and its harmonics are marked on the spectrum.
3
Match bearing frequencies
The envelope spectrum is taken from the most impulsive band. Peaks that match BPFO, BPFI, BSF or FTF are listed as candidates.
1
Data
Pick a record. All are mathematically generated examples, not real plant data.
My own vibration record
Drop a CSV or TXT file here
Pick one numeric column; if there is a time column, the sampling rate can be inferred from it.
2
Settings
The window and FFT length they change.
Example bearing (deep-groove, illustrative): check your bearing’s data sheet and enter your own values.
- RMS
- Effective size of the signal; relates to energy.
- Peak
- Largest absolute value.
- Impulsiveness: about 1.41 for a pure sine.
- About 3 for Gaussian noise; impacts raise it.
- Envelope kurtosis
- Impulsiveness of the envelope; rises with a defect.
Waveform
First 0.25 seconds, mean and trend removed. Drag to zoom.
Amplitude spectrum
Each line is a frequency component; its height is the amplitude. Dashed lines are running-speed harmonics; coloured lines are bearing frequencies. Drag to choose the envelope band.
Spectrogram
Time left to right, frequency bottom to top; brighter means stronger.
Bright cells are impulsive bands; the brightest one is used for the envelope. Each row has more bands as the level rises.
Envelope spectrum
Impact repetition frequencies. A bearing defect shows a peak at frequencies such as BPFO or BPFI.
Overall velocity RMS (10–1000 Hz). The needle shows the zone against your boundaries.
What this suggests
These are hints, not a diagnosis.
The decision is the engineer’s. For the limits, see the reading note.
Strongest 8 peaks
f/fr is the ratio to running speed. A match is written when the peak is near a harmonic or bearing frequency.
| # | Hz | Amplitude | Match |
|---|
Nominal values. Enter your catalogue data.
| Component | Hz |
|---|
Export
How do I read the result?
- 1Verdict card. Colour and wording together give the state: Normal, Watch or Attention. It sets a priority; it is not a diagnosis.
- 2Spectrum. 1×, 2× and 3× lines are running-speed harmonics. Bearing frequencies have their own colours. Drag to select a band.
- 3Kurtogram and envelope. The band of the brightest kurtogram cell is applied to the envelope. Peaks at BPFO, BPFI, BSF or FTF and their multiples are listed as candidates.
- 4Severity. The overall velocity RMS is compared with the A/B, B/C and C/D boundaries you enter. The defaults are illustrative; enter the ISO 20816 limits for your machine class.
- 5What a match means. It is only a frequency match. Confirm with trend, temperature, oil analysis and inspection.
Spectra gives hints, not a diagnosis. Bearing frequencies are nominal: slip can shift real peaks by a percent or two. The sampling rate and the accelerometer bandwidth limit the usable range, so check mounting and the sensor’s frequency range. An acceleration record suits envelope analysis best.
Frequently asked
What files and units does Spectra accept?
A CSV or TXT file, or a table pasted as text. You choose one numeric column as the signal. Enter the sampling rate in Hz, or let it be inferred from a time column in seconds or milliseconds. The unit can be g, m/s² or mm/s. At most 16,384 samples are analysed; longer records use their first 16,384 samples.
Why an envelope spectrum?
A rolling-element defect makes a short impact at each contact. The impacts excite a high-frequency structural resonance. The envelope extracts how that resonance’s amplitude changes, so the repetition rate of the impacts, such as BPFO or BPFI, shows directly in the envelope spectrum. It is a way to separate the defect frequency from high-frequency noise.
Why velocity for overall severity and acceleration for bearings?
Overall severity scales use the RMS of vibration velocity, which relates to the energy that causes wear and heating. Bearing defects appear as short impacts at high frequency, which an accelerometer captures better. Spectra derives velocity from acceleration by dividing each component by 2πf.
Is a zone A–D a diagnosis?
No. The zones only place the overall velocity value relative to the boundaries you enter. The default boundaries are illustrative and do not represent ISO 20816; enter the limits for your machine class from the standard yourself. A zone does not say what the cause is.
Is my data uploaded?
No. The record is processed in your browser by a WebAssembly module written in C. Nothing is sent anywhere, and the record is gone when you close the page. The CSV, JSON and PNG files you export stay with you.
Go deeper.
Full library
Instrumentation
How to read an FFT spectrum: resolution, windows, peaks
After reading, you can compute frequency resolution for a vibration record, justify your window choice, and read spectral peaks as clues rather than diagnoses, using a worked example.
Instrumentation
Envelope analysis for rolling bearing faults: steps and frequencies
This article shows how envelope analysis pulls repeating impacts out of a high-frequency vibration band, how to calculate the four defect frequencies, and how to read the result step by step.
Instrumentation
Nyquist and aliasing: how fast to sample sensor data
After reading, you can set a sampling rate from your analysis band, recognise a false low-frequency peak caused by aliasing, and see why slow PLC or SCADA logs fall short for spectra.
Instrumentation
ISO 20816 vibration severity zones: how to use them and where not to
After reading, you can track a machine's broadband vibration against its own baseline and read the ISO 20816 zones in the right context, without treating a zone as a fault diagnosis.
Related questions
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