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Noknroll

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Reply with quote  #1 
Hoping someone here can work out whats going on.

Measuring bearings on a couple of horizontal drum mixers at 36 rpm

AP set is peakvue, 80X 1600 lines and 500Hz HP filter

Machine 1 data looks like this
1.png 

and has looked the same since measuring started
2.png 

While machine No:2 with same AP setup looks normal
3.png
A
ny ideas?
Thanks

David Eason

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Reply with quote  #2 
Noknroll,
What's the big hit every 6 revs? 2 G's seems a bit too much for something turning 36 rpm. I'm guessing machine 2 doesn't have it? I would think that's why your data looks different.

David
Shoveldr

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Reply with quote  #3 

What does the normal data look like? Specifically over that 500Hz HP Filter.

You may need to increase your HP filter for Peakvue. 

Are these permanently mounted sensors or are you using a sensor with a magnetic base?

Danny Harvey

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Reply with quote  #4 
I'm not sure how this relates to your setup but every time I have seen this similar pattern it has been a bad cable.  The pulse was provided by a tunable strobe. Others may have a better explanation for why but I have monitored two channels  while using the strobe and the pulse disappears when the strobe is off and it follows the bad cable.  Replaced the cable and it went away.  

It used to happen all the time when I was using the 2120-2 and collecting data with two accels and the 628 adapter. The BNC connector on the B channel cable would last about 6 weeks.  I fought it for a while and then discovered a tiny little company that was giving out a ridiculous warranty for replacement stuff and never had another failure.

Is there something that may generate a pulse like that?  Maybe someone can tells us what might.
RustyCas

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Reply with quote  #5 
As an aside, that “tiny little company” isn’t what it used to be. I needed the cable that connects my 4-channel adapter to my 2140 to be 2” longer because the original from CSI failed due to strain at the connectors. The “tiny little company” had it, but it was an exact duplicate of the CSI cable. They couldn’t manufacture it 2” longer because of the “engineering” that would be needed to change the cable per ISO requirements. So....
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Vibe-Rater

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Reply with quote  #6 
I would get on to CTC Rusty, they make so many CSI cables and come with lifetime warranty. rgds
Danny Harvey

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Reply with quote  #7 
John,

CTC WAS the tiny little company. 

The have a custom cable builder app on their site. I'm not sure why Rusty got the run-around but I expect that it's got something with them being not-so-tiny anymore.
RustyCas

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Yes, CTC.  Still a great company, but if a cable is not available on the Cable Wizard, then they won't modify it.  The 2140 4-channel adapter cable is a "standard" item, and apparently can't be modified without a considerable engineering effort to modify all the ISO documentation.  Understandable, but frustrating when a 9" cable cost $205.

I still get all my cables from CTC, and will continue to do so.  They do have the connector now for the CSI triaxial sensor, and I was finally able to get that "coiled" cable I wanted for walk-around use. Works well.

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Jim Crowe

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Reply with quote  #9 
I would take a 40 order, 3200 LOR, 500 Hz HP and look for the approximately every 6 rev frequency. Zoom in on the first part of the spectra you have and see if all of the harmonics are this lower frequency event.
Noknroll

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Reply with quote  #10 
Jim,
If you look at the spectrum in the top attachment, before posting i zoomed in and marked the difference between the peaks. See dfrq in pink text 0.0938 Hz. Close enough to be called 1 sixth X rpm
Shoveldr
I will post some normal data next time I'm on my work pc, its a portable magnetic accel

I cant think of anything nearby that would be transmitting 6cpm impacts

Danny I'm confident my cables are ok, this is the only machine and point displaying this odd looking data
Danny Harvey

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Reply with quote  #11 
Nok,

I thought it was an on-line system with permanent accels and cables. I must have gotten this thread mixed up with another about a CSI 6500 system.

Sorry for the distraction.
Sinski

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Reply with quote  #12 
Nok. Just a long shot. If you have a chance try and collect some data with a thin piece of plastic between your magnet and the machine. I have come across some odd data that was caused by stray currents that looked like that. I could be wrong but I think its worth a shot.
Noknroll

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Reply with quote  #13 
Sinski
Worth a try, I'll give it ago, next time on site mid october

and the normal data taken at the same time as peakvue
4.png

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