Skip to main content

Reply to "doubts of VA"

Hello K.
1) THe frequencies must be calculated by substituting (Rpm of Inner ring - Rpm of Outer) for Rpm in the traditional formulas i.e.:

BPFO frequency= (Nb/2)*(1-Bd*CosA/Pd)*(Rpm of Inner ring-Rpm of Outer ring)
where Nb= Number of Balls or Rollers, Bd= Ball or roller Diameter, A= Contact angle, Pd=Pitch diameter

2)1x Sidebands means that the 1x vibration is significant and coexistent when the BPFI or BPFO frequency is present. If BPFO or BPFI vibration intensity increases and decreases in synch with the shaft speed, sidebands will be created by the FFT. The cause of the 1x vibration can be numerous. "Looseness" is only possible reason.

3) Frequency of the vibration signal will be as accurate as the instrument and its setup will allow. For example, The accelerometer can not make a 70khz signal display as a 75khz signal or any thing other than 70khz. As you have said the intensity of the signal may be compromised greatly because of the physical characteristics of the accelerometer. You can use an accelerometer above its 3dB rolloff rating with no problem. Never use an accelerometer above its rated resonant frequency- the attenuation is above 90%.
×
×
×
×