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FFT Analyzer

Frequency analysis is the base for any NVH task. The FFT analyzer in Dewesoft has it all: top performance, advanced cursor functions, very high freely selectable line resolution, flexible averaging as well as many advanced functions for in-depth analysis.

Strain / Stress
Strain / Stress
High-speed video
High-speed video
Thermal video
Thermal video

Main Features

  • ANY LINE RESOLUTION: selectable line resolution up to 64000 lines for most demanding tasks
  • CURSOR VALUE ESTIMATE: innovative window interpolation technique allows precise amplitude and frequency estimation
  • CURSORS AND MARKERS: maximum marker, free marker, zoom marker, sideband marker, harmonic marker
  • AVERAGING: block history with linear, peak, exponential averaging or overall calculation
  • ADVANCED MATH: auto spectrum, cross spectrum, complex spectrum, waterfall spectrum, cepstrum (for bearing faults, speech processing), two-sided full FFT (for rotor whirl analysis), STFT (for non-stationary signals), envelope detection (for bearing fault analysis)

Multipurpose cursors

The Dewesoft FFT analyzer allows setting multiple markers for automatic detection of different parameters. The following markers are available:

  • Free marker - shows us the frequency of the peak at which it stands and its amplitude
  • MAX marker -  finds the highest amplitude in the spectrum
  • RMS marker - sum up all the FFT lines in the selected band and calculates the RMS value​​​​​​​
  • Sideband marker - monitors the modulated frequencies to the left and right from the selected center line
  • Harmonic marker -  identifying the fundamentals of the frequency (marker will mark the harmonics of the selected frequency)
  • Damping marker - calculates how our curve is damped. We select it when we are interested in the quality factor, damping ration or attenuation rate of a selected peak
  • Bearing cursor -  identify the bearing frequencies (envelope detection)


FFT settings

The Dewesoft X FFT analyzer module allows several parameters to be set up before the calculation:

  • Output channels - complex, amplitude, overall RMS
  • Calculation type - block history or overall
  • Windowing - Rectangular, Hanning, Hamming, Flattop, Triangle, Blackman, Exponent down, Transient
  • Resolution - up to 64000 lines
  • Amplitude type - peak, peak-peak, RMS, PSD, Power
  • DC cutoff - remove DC or low-frequency components
  • Overlap - define the percentage of time signal that has already been calculated and it is used again for calculation
  • Weighting - calculate the sound weighting in the frequency domain (A, B, C, D)
  • Averaging type - linear, exponential, peak-hold

Bearing fault detection

Envelope detection is a procedure for early detecting of faults on ball bearings.

When an error of the ball bearing occurs, it will produce ringing with a frequency which corresponds to its natural frequency. This ringing will repeat each time when a damaged part of the ball hits the ring or vice versa. We have to know also that inner ring, outer ring, cage and balls have different typical repeating frequency depending on the geometry of the bearing and the rotational frequency.

STFT - Short Time Fourier Transform

STFT is a well-known technique in signal processing to analyze non-stationary signals. STFT is segmenting the signal into narrow time intervals and takes the Fourier transform of each segment. 

When the signal changes fast, you need small time to calculate frequency spectrum faster. But you still want better frequency resolution and here STFT comes in place (we get 16 times better frequency resolution for the same time frame.).


Full Spectrum

Used for signal modulation, signal demodulation, and rotor whirl analysis. 

  • the single value or block history
  • windowing
  • overlap and DC cutoff


The cepstrum calculation (also used to determine characteristics in speech analysis) helps to identify vibration signatures, such as frequencies in gearbox and bearing analysis. Dewesoft provides mirror spectrum, low and high frequency output.

  • selectable block size
  • windowing
  • liftering
  • overlap and averaging

Video on the right side shows Cepstrum math being used on a microphone input signal to determine the speaker name.

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