BERAN

Proven Condition Monitoring Solutions

Glossary

  • E

    • Excitation

      A complex mechanical drive train system, such as that found in a helicopter, generates a wide range of vibration forces at their fundamental rotational frequencies and harmonics. These are termed excitation forces which can be imparted into the airframe structure.

    F

    • FFT

      The Fast Fourier Transformation is an algorithm named after Jean Baptiste Joseph Fourier (Born: 21 March 1768 in Auxerre, Bourgogne, and died on 16 May 1830 in Paris, France). In essence, it decomposes or separates a complex waveform or function into sine waves of different frequency which sum to the original waveform. It identifies or distinguishes the different frequency sine waves and their respective amplitudes.

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    • Filter

      A filter is an electrical circuit which is specifically designed to attenuate or eliminate unwanted frequencies from a broad range of frequencies. They are usually described as Low Pass, Band Pass and High Pass Filters.

    • Frequency

      The frequency of a Sine Wave is the count of the number of cycles performed in a defined period of time. It is commonly measured in ‘Hertz’ (Hz) which are ’cycles per second’ or ‘cycles per minute’ (CPM).

    G

    • Gear - Mesh Frequencies

      In addition to their fundamental rotational frequencies meshing gears produce a vibration which is the product of the number of teeth and their rotational frequency and is an indication of machine health. For example a 61 tooth gear rotating at 1705.5 rpm meshes with a 17 tooth gear. The 17 tooth gear will rotate at (61/17)*1705.5 = 6120.09 rpm. The dominant frequencies will be 28.4 Hz and 102.0 Hz for the fundamental rotational frequencies and a gear-mesh of 1734.0 Hz.

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