Someone can hear me, please???? Order Analysis Toolkit: information about the compensation for "Reference Signal Processing", which is scarce in the manuals, the website and the examples installed with the toolkit.

[CracKatoA]

Someone can hear me, please????

 I am using the Order Analysis Toolkit and want to get more information about the compensation for "Reference Signal Processing", which is scarce in the manuals, the website and the examples installed with the toolkit.

In particular, I am analyzing the example "Even Angle Reference Signal Processing (Digital Tacho, DAQmx).vi", whose documentation I am reproducing in the following:

<B>DESCRIPTIONS</B>:
This VI demonstrates how to extract even angle reference signals and remove the slow-roll errors. It uses DAQmx VIs to acquire sound or vibration signals and a digital tachometer signal. This VI includes a two-step process: acquire data at low rotational speed to extract even angle reference; use the even angle reference to remove the errors in the vibration signal acquired at normal operation.

<B>INSTRUCTIONS</B>:
1. Run the VI.
2. On the <B>DAQ Configurations</B> tab, specify the <B>sample rate</B>, <B>samples per channel</B>, device and channel configurations, and tachometer channel information.
<B>NOTE</B>: You need to use DSA PXI-447x/PXI-446x and PXI TIO device in a PXI chassis to run this example. The DSA device must be in slot 2 of the PXI chassis.
3. Switch to <B>Extract Even Angle Reference</B> tab. Specify the <B>number of samples to acquire</B> and the <B># of revs in reference</B> which determines the number of samples in even angle reference. Click <B>Start</B> to take a one-shot data acquisition of the vibration and tachometer signals. After the acquisition, you can see the extracted even angle references in <B>Even Angle Reference</B>.
4. Switch to the <B>Remove Slow-roll Errors</B> tab. Click <B>Start</B> to acquire data continuously and view the compensate results. Click <B>Stop</B> in this tab to stop the acquisition.

<B>ORDER ANALYSIS VIs USED IN THIS EXAMPLE</B>:
1. SVL Scale Voltage to EU.vi
2. OAT Digital Tacho Process.vi
3. OAT Get Even Angle Reference.vi
4. OAT Convert to Even Angle Signal.vi
5. OAT Compensate Even Angle Signal.vi

My question is: How is the synchronization produced at the time of the compensation ? How is it possible to eliminate the errors in a synchronized fashion with respect to the surface of the shaft bearing in mind that I am acquired data at a low rotation speed in order to get the "even angle reference" and then I use it to remove the errors in the vibration signal acquired at normal operation. In this application both operations are made in different acquisitions, therefore the reference of the correction signal is lost. Is it simply compensated without synchronizing ?

Our application is based on FPGA and we need to clarity those aspects before implementing the procedure.

Message Edited by CracKatoA on 06-25-2007 03:10 PM

Message Edited by CracKatoA on 06-25-2007 03:11 PM

[preston_johnson · Accepted solution]

The purpose of run-out compensation is to remove deformities in the shaft that might otherwise appear as vibrations.  Examples include out of round shaft, nicks in the shaft, or some other abnormality that a proximity probe might see as a vibration.

There are two methods of "run-out compensation".  Both use a reference of data collected when the machine is running slowly (also called slow roll compensation). 

The first is vector based, at slow roll the phase and magnitude of vibration data (typically 1 times and two times (1x and 2x)) is calculated.  During the run of the machine, these values are vector subtracted from the phase and magnitude measurements made at run time. 

The second is angle based.  Here slow roll time series data is collected and stored.  The angular (synchronously sampled values) base data is subtracted point by point at the appropriate degree of rotation from the new synchrounously sampled data.  In the OAT tools we refer to synchronously sampled data as even-angle sampled data. 

In either case, both methods remove the imperfections of the shaft that otherwise would appear as vibration data collected from a proximity probe. 

Let us know what other questions you have.