06-02-2008 01:59 PM
06-02-2008 09:48 PM
06-06-2008 11:17 AM
06-09-2008 02:20 PM
Hello Leachdor,
It sounds like your calculation is different from Preston's in that yours is an average max/min where as his is strictly the max/min. It is really up to you whether or not you want to average or not. If you're looking for the "overall vibration value" the average is probably more representative than the max/min.
If you're performing the same analysis on all for channels then it’s likely that you don't need to split the signals as many VI's are able to automatically adapt to multiple channels. If you find that some of the analysis VI's you're using do require a single signal input then you should be able to use the split signals VI to split the signals. In order to do this you'll need to put a Split Signals VI on the block diagram and then expand the VI to have 4 outputs by hovering your mouse over the bottom edge of the VI. Once you're hovering there you can click and drag the lower edge of the VI to expand the number of output.
I hope this helps, and if you still have trouble with this feel free to post back with more questions.
Cheers,
06-10-2008 07:45 AM
06-11-2008 03:59 PM
Hello Leachdor,
It is difficult to diagnose why the results vary, but here is how I would approach it. I would assume that if you pass the same data set to the analysis VIs then you'll always get the same values. That means that if your result is different than your input signals aren't always the same. I would recommend using some graph indicators on your VI to view the signals at each stage of your VI to make sure they're what you expect. If you have some very low frequency vibrations it’s also possible that phase discontinuities are playing a role, but this will be apparent in the graph indicators.
Also, are you saying the same reference sensor read the same value every time (within a few thousandths of the expected value), and that you have another sensor that reads 16% off? Or are you saying that the reference sensor read within a few thousandths the first time and about 16% off in subsequent runs?
In either case I would recommend looking at the input signals in both cases as this is likely the source of the resulting disparity. Once you know what the difference is between the signals it will be easier to diagnose the problem or modify your analysis to account for the difference in your signals.
Cheers,