Condmaster Ruby Module Run Up/Coast Down, Bump Test, FRF
The MOD137 features run up/coast down measurements, Bump test and FRF vibration analysis functions offered as a module for Leonova and Intellinova.
Run up/coast down records the changes in vibration while the machine is run up to operating speed or after it has been shut off and is slowing down. For this test, both the signal unit and the unit for the spectrum can be selected. The measuring interval can be either time based (interval in seconds) or speed based (interval in rpm). The speed range is also chosen, e.g. 400 to 3000 rpm.
Waterfall diagram can be viewed after the measurement is done. For each individual measurement, a spectrum can be called up.
Nyquist diagram shows the phase angle and amplitude. A phase is a time delay expressed in degrees of rotation. Leonova calculates the time delay between the passage of the tachometer pulse and the peak of the frequency component of interest from the vibration transducer at the speed of rotation. The value presented is a relative angle, not an absolute, because there is no compensation for phase lag in the transducer or the electronic circuits.
Bode diagram can be selected for vibration amplitude and angle, showing all measurements in time sequence. In all diagrams, a blue dot shows the position of the measurement marked on the list.
Bump test is employed to check out the typical vibration response of a machine structure at standstill, by hitting it e.g. with rubber mallet (bump test). The user sets the measuring range in Hz, which automatically sets the sampling time, e.g. 0.20seconds for 2000Hz/400 lines. A pre-trigging time, 5% to 25% of the sampling time, is also chosen. The peak amplitude of the measured signal is displayed (velocity in mm/s) and a trigger level can be set to 1% - 90% of the amplitude.
The actual test returns an FFT spectrum and a time signal (sampling time plus pre-trigging time). The spectrum can be stored as reference spectrum for any measuring assignment.
Frequency Response Function (FRF) is used to measure the vibration response (natural frequencies) of a machine structure, similar to the ‘Bump test’. FRF however is more sophisticated, measuring the response resulting from a known applied input by using an impact hammer and a vibration transducer connected to Leonova Diamond’s vibration input using a split cable.
The FRF measuring assignment is set up in Leonova Diamond and the settings and measuring results can be viewed in Condmaster Ruby after the measuring round is uploaded.