Im' working on a balancing machine. this machine has two vibration sensors. (pizzo) my question is about that why this machine use two Sensors? this machine has an rotary encoder to detect disk angle.

i trying to read these signal by ADC card and using FFT bandpass filtering to calculate unbalanced mass on disk. for this algorithm i just use one of Vibration sensors. should i use second sensor?

Machine schema

  • $\begingroup$ Can you please provide a little bit more information about the equipment? Maybe the reason for two sensors is a technical one (?) $\endgroup$
    – A_A
    Commented Jan 12, 2017 at 16:32
  • $\begingroup$ this machine use to finding unbalancing mass on plastic Fan. when fan placed on this system, Start the spinning speed about 1500 rpm. after a while, system shows unbalanced mass and it's angle.(like 1.21 gr at 305 ) $\endgroup$ Commented Jan 12, 2017 at 16:40
  • $\begingroup$ Can the sensor output to be added together or subtracted? $\endgroup$ Commented Jan 13, 2017 at 12:03
  • $\begingroup$ This is what I thought it might be doing internally. Otherwise, the signal of the two sensors will have a constant phase shift depending on RPM. Are you sure that both sensors are mounted on the same axis? $\endgroup$
    – A_A
    Commented Jan 13, 2017 at 14:03
  • $\begingroup$ yes, there are mounted on same axis. there is only phase shift between two sensors. $\endgroup$ Commented Jan 13, 2017 at 14:24

1 Answer 1


Of course, the machine could be provided with three, four or more sensors, if the goal of the control unit is perform a balancing of the rotation. Actually three sensors should be the proper selection if the rotation is unconstrained in a biaxial plane, and two sensors, if constrained in a uniaxial direction.


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