Performing a Torsional Vibration Measurement (Sound and Vibration Measurement Suite)
December 2007
NI Part Number:
372416A-01
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The following example demonstrates how to use the Torsional Vibration Measurement VIs to measure torsional vibration in a rotating system.
The device under test (DUT) is a rotating system with an electric motor as the driving force. The critical torsional frequency of the system is around 12 Hz. The electric motor applies a 12 Hz excitation force to the rotating system. When the excitation torsional frequency equals the critical torsional frequency, the rotating system generates the strongest torsional vibration. Use the Torsional Vibration Measurement VIs to measure the torsional vibration from the rotating system. If the torsional vibration signal has a large amplitude at 12 Hz, you verify that the torsional vibration of the rotating system is strong.
An optical transducer obtains the tachometer signal from the system. The optical transducer generates 28 pulses per revolution. The following figure shows the tachometer signal you obtain from the DUT.
Use the OAT Torsional Vibration (Analog Tacho) VI to calculate the torsional vibration signal from the tachometer signal. Because the DUT generates torsional vibration at a fixed frequency, use the Waveform Out 1 Channel instance of the OAT Torsional Vibration (Analog Tacho) VI to calculate the torsional vibration signal. Because the optical transducer generates 28 pulses per revolution, set pulse/revolution to 28. Set compensate geometric imperfection? to TRUE to compensate for any geometric imperfections of the tachometer system. Run the VI to acquire the torsional vibration signal from the tachometer signal.
Use the SVFA Power Spectrum VI to measure the power spectrum of the resulting torsional vibration signal, as shown in the following figure.
Notice that the Power spectrum plot contains only one peak around 12 Hz. This value is the same as the excitation frequency and the critical torsional frequency. From this peak, you can see that when the excitation frequency coincides with the critical torsional vibration frequency, the torsional vibration of the system is strong.
Refer to the following VIs for examples of performing torsional vibration measurement with the Torsional Vibration VIs.
- Torsional Vibration Measurement (Analog Tacho) VI: labview\examples\Order Analysis\Torsional Vibration
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- Torsional Vibration Measurement (Digital Tacho) VI: labview\examples\Order Analysis\Torsional Vibration
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