What is a Bode Plot in Oliver Advanced Software?
OLIVER stands for On-Line Investigation of Vibration in Equipments and Rotary Machines. It is a software Homegrown by IRD Mechanalysis Limited and its advanced version helps in performing Vibration Measurement and Analysis.
As a part of its standard offering - OLIVER Advanced allows capture of Bode Plot. This is a 2 Dimensional Plot that is a combination of 2 Plots captured simultaneously - the first being Vibration Amplitude vs Speed (Frequency) and the second being Phase vs Speed (Frequency).
Since speed is involved - a Bode Plot is usually captured from either Zero Speed to Full Speed (called as 'Run Up') or Full Speed to Zero Speed (called as 'Coast Down'). Detection of Speed requires a Tachometer (usually a laser tachometer) - but in the absence of a Tachometer - time based capturing is also possible.
Oliver Advanced uses data from Phase Reference Sensor (looking at a notch), Tachometer and Vibration Sensor together to generate the Bode Plot. A Data Acquisition Unit like NI cDAQ acquires the data which is post processed in Oliver to generate the Plot.
Bode Plot is used by Vibration Analysts to detect Resonance and find out the Natural Frequency (speed or frequency at which vibration spikes). It is a practice to keep operational speed away from Resonance Speed. In a Bode plot, at resonance condition - vibration increases suddenly and phase changes by 180 degrees approx