Vibration measurements of rotating shafts and discs are often performed using non-contact transducers. Measurement setups that employ non-contact displacement transducers have been widely used in industry and non-contact measurement became especially popular with the advent of LASER operated velocity transducers. Mounted directly on ground or on stationary parts of machines, these transducers measure the motion of a rotating shaft relative to a non-rotating coordinate system. Measurement of accelerations relative to a non-rotating coordinate system is also not uncommon using a slip-ring like mechanical apparatus. This device provides a non-rotating platform, where attached accelerometers measure the bending accelerations of a rotating shaft relative to a non-rotating coordinate system. A common advantage of all these measurement techniques is the ease of instrumentation which saves time and reduces cost.
The data collected using the measurement methods described above is affected by a coordinate transformation which changes its spectrum. The spectral changes occur at both frequency and amplitude. The frequency change is manifested as the shifting of spectral components to higher and/or lower frequencies by a frequency equal to the rotational frequency of the shaft. The amplitude changes, on the other hand, depend on the phase relationship between the vibrations of the shaft (or disc) in the two orthogonal directions of its, body-fixed, rotating coordinate system. This interesting phenomenon is known as Order Transfer or Order Shift.
In many cases, it is necessary to obtain the vibration spectrum of a shaft (or disc) relative to its body-fixed coordinate system. For instance, quantities such as the static deflection and bending resonance frequency of a rotating shaft can only be extracted from data in a body-fixed coordinate system. Furthermore, estimating the shear force or the dynamic moment acting on the interface of a shaft and its flywheel also requires any data measured in a non-rotating coordinate system is transformed to a body-fixed coordinate system. Needless to say, such vibration spectra can be directly measured. However, it is more cost efficient and less time consuming to prepare non-contact measurement setups and transform the measured data to a rotating coordinate system.
The Order-X Module of the MIDA System is designed to perform such coordinate transformations. Order-X transformations can be made from non-rotating to rotating or from rotating to non-rotating coordinate systems. The measured data could be in time, frequency, angle or order domains. Furthermore, displacement, velocity or acceleration data can be transformed.
The links on the left lead to pages where the user interfaces of the Order-X Module and their features are introduced. You can also download a technical paper or an application note on Order Shift using the links on the right hand side of this page.
If you would like to try out the Order-X Transforms and get first hand experience with the features of the Order-X Module you can download the MIDA System for a free-of- charge evaluation. Just follow the link Download MIDA on the left.
Download a technical paper
on Order Shift (pdf)
Download an application note
on
Order-X
(pdf)
