FFT Applications

FFT         Vibration analysis

V-1-1      Measuring natural vibration frequency and damping ratio by hammering test

  • This example shows how to measure natural vibration frequency and damping ratio etc. Suspend a measurement object in a free vibration (or place it on something soft) and perform hammering test by the GK-3100 Impulse hammer. And then detect the free damping vibration by an accelerometer. The DS-5000 series calculates the frequency response function of acceleration (A) and hitting force (F) by applying them to the following calculation, and obtains the resonant frequency at the peak of (A) / (F). (In this example, the peak value of (A)/(F) equals to the resonant frequency, natural vibration.)
  • Frequency response function = Acceleration (A) / Hitting force by the GK-3100 (F) (Accelerance < Inertance >)
  • You can see several peak values depending on a shape of a measurement object. Damping ratio also can be calculated by using half-power bandwidth method. sMoreover, integrating function of the DS-5000 series enables display and evaluation of velocity/power (mobility), displacement/force (compliance), force/acceleration (dynamic mass), force/velocity (mechanical impedance) or force/displacement (dynamic rigidity).

Product list

  Model Product name Remarks Qty
1 DS-5000 O-Solution 3ch 40 kHz FFT set DS-5100 Main Unit
DS-0523 3ch 40 kHz Input Unit
OS-5100 Platform
OS-0522 FFT Analysis Function
OS-0512 Hardware Connecting Function		 1
2 GK-3100 Impulse force hammer Frequency range:: up to 8 kHz, resonance frequency: 31 kHz, hammer cable (3 m) & signal output cable (0.9 m) (included) 1
3 NP-3412 Accelerometer with built-in preamplifier Ultra compact, lightweight (0.5 g), frequency range: 0.3 Hz to 20 kHz ±3dB, signal cable (3 m) (included) 1
4 NP-0151A Signal cable 1.5 m Compatible Sensor Models:NP-2910/NP-3110/NP-3412/NP-3414/NP-3418
Cable diameter : φ1.2 mm
Type : Low noise cable		 1
5 NP-0021 Miniature / BNC Conversion Adapter NP-0153A Converts the NP-0153 signal cable terminal to BNC connector and input to the DS-5000 series BNC connector. 1

Remarks
The DS-5000 series needs a PC separately.
The DS-5000 series data stations "FFT Tracking Set", "FFT Octave Set", and CF-9200A / 9400 can also be used as analyzers.





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