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Rotating machinery analysis - order tracking
3

Rotating machinery analysis - order tracking

Rotating machinery analysis - order tracking

(OP)
People,

How do you do your order analysis?  Do you use synchronous sampling (or resampling) using a tach signal?  Or do you simply acquire narrow band spectra and then extract the orders by summation across a number of bins?

It's been a while since I last did this sort of thing in the lab and times/practices do change.

- Steve

RE: Rotating machinery analysis - order tracking


I use synchronous sampling. I enter the info of the tach with a NI acquisition card where I also connect the accelerometers.  

RE: Rotating machinery analysis - order tracking

We don't use synchonous sampling.   (In fact I hadn't heard of that..not sure I understand why it would be needed).

We simply get high enough frequency resolution (long enough sample duration) to give us confidence in our frequency estimate of the relevant peaks.   Additionally, there are techniques to resolve frequencies to a precision much better than the bin width in most cases as discussed here
thread384-208992: "Interpolating" to estimate exact frequency of peak from FFT results

We use E-monitor software which makes these tasks relatively easy.  

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RE: Rotating machinery analysis - order tracking

I just realized maybe you guys are talking about transient analysis (coastdown) ?

If so, then .... never mind purpleface
(disregard my comments)

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RE: Rotating machinery analysis - order tracking

sometimes people do vib measurement during acceleration too...
 

RE: Rotating machinery analysis - order tracking

If you've got fast slew rates it can give you a better signal (or it can be worse), and it has the advantage that the phase of the signals relative to the clock is easier to understand, I think. Balancing machines are often synchronous, probably for this reason. Also your data files tend to be smaller.

For driveline work I could be persuaded either way, but for engine noise I would stick with frequency based analysis. A lot of engine noise work is based on subjective assessments, you can't listen to a synchronous signal (well you can but it would be very odd).
 

Cheers

Greg Locock

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RE: Rotating machinery analysis - order tracking

(OP)
I should have been clearer, sorry.  This is (quasi-steady) transient analysis of engine (intake/exhaust to be precise) noise.  Typically a slow run up or down.

From the replies so far, it sounds like there is no clear consensus.

- Steve

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