diff between SPM and full spectum

[nisqually]

Can someone tell me what the difference between shock pulse monitoring and full spectrum analysis is in practical terms? I believe spm is used exclusively for monitoring bearing condition. FFT instruments can be used for finding additional problems such as shaft misalignment, belt looseness, etc? I appreciate any information. Thanks.

 

[electricpete]

I assume that Shock Pulse is similar to other demod methods.

In general the demod methods are useful for detecting periodic repeating impacting-type of events, including bearing defects.

You are correct these methods won't detect lower frequency symptoms associated with unbalance, misalignment etc. The algorithm first step filters out the low frequency components, then takes a time envelope of the remaining high frequency stuff, then applies dft.

I think most people would agree that the demod methods shouldn't be used by themselves. They provide a good early warning. The defects are easier to see with the demod method. Then close evaluation of the regular spectrum helps to confirm the severity.

I believe that most programs use both methods together.