Vibration Analysis Tech Tip: Scale Your Graphs!

www.DLIengineering.com
Posted 11-22-04

The human mind is excellent at pattern recognition and you can easily train it to quickly scan vibration spectra and identify machine faults. The trick however is to always use the same vertical scale on your graphs. Those of us who use VdB units typically scale our graphs either from 60 to120 VdB or 70 to 130 VdB. In/s units are often scaled from 0 to 0.5 in/s.
The problem with using "auto scale" on your graphs is that this function always places the highest peak at the top of the graph scale. Therefore you never have a grasp of the relative amplitude of the peak without actually placing a cursor on it. We at DLI look at hundreds of graphs a day, year in and year out. Take our word for it, if you always use the same scale on your graphs you'll greatly speed up your analysis work and you'll train your mind to recognize fault patterns.